time

package standard library
go1.23.3 Latest Latest
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 Go to latest Published: Nov 6, 2024 License: BSD-3-Clause Imports: 8 Imported by: 2,332,859

Documentation

Overview

Package time provides functionality for measuring and displaying time.

The calendrical calculations always assume a Gregorian calendar, with no leap seconds.

Monotonic Clocks

Operating systems provide both a “wall clock,” which is subject to changes for clock synchronization, and a “monotonic clock,” which is not. The general rule is that the wall clock is for telling time and the monotonic clock is for measuring time. Rather than split the API, in this package the Time returned by time.Now contains both a wall clock reading and a monotonic clock reading; later time-telling operations use the wall clock reading, but later time-measuring operations, specifically comparisons and subtractions, use the monotonic clock reading.

For example, this code always computes a positive elapsed time of approximately 20 milliseconds, even if the wall clock is changed during the operation being timed: 

start := time.Now()
... operation that takes 20 milliseconds ...
t := time.Now()
elapsed := t.Sub(start)

Other idioms, such as time.Since(start), time.Until(deadline), and time.Now().Before(deadline), are similarly robust against wall clock resets.

The rest of this section gives the precise details of how operations use monotonic clocks, but understanding those details is not required to use this package.

The Time returned by time.Now contains a monotonic clock reading. If Time t has a monotonic clock reading, t.Add adds the same duration to both the wall clock and monotonic clock readings to compute the result. Because t.AddDate(y, m, d), t.Round(d), and t.Truncate(d) are wall time computations, they always strip any monotonic clock reading from their results. Because t.In, t.Local, and t.UTC are used for their effect on the interpretation of the wall time, they also strip any monotonic clock reading from their results. The canonical way to strip a monotonic clock reading is to use t = t.Round(0).

If Times t and u both contain monotonic clock readings, the operations t.After(u), t.Before(u), t.Equal(u), t.Compare(u), and t.Sub(u) are carried out using the monotonic clock readings alone, ignoring the wall clock readings. If either t or u contains no monotonic clock reading, these operations fall back to using the wall clock readings.

On some systems the monotonic clock will stop if the computer goes to sleep. On such a system, t.Sub(u) may not accurately reflect the actual time that passed between t and u. The same applies to other functions and methods that subtract times, such as Since, Until, [Before], After, [Add], [Sub], [Equal] and [Compare]. In some cases, you may need to strip the monotonic clock to get accurate results.

Because the monotonic clock reading has no meaning outside the current process, the serialized forms generated by t.GobEncode, t.MarshalBinary, t.MarshalJSON, and t.MarshalText omit the monotonic clock reading, and t.Format provides no format for it. Similarly, the constructors time.Date, time.Parse, time.ParseInLocation, and time.Unix, as well as the unmarshalers t.GobDecode, t.UnmarshalBinary. t.UnmarshalJSON, and t.UnmarshalText always create times with no monotonic clock reading.

The monotonic clock reading exists only in Time values. It is not a part of Duration values or the Unix times returned by t.Unix and friends.

Note that the Go == operator compares not just the time instant but also the Location and the monotonic clock reading. See the documentation for the Time type for a discussion of equality testing for Time values.

For debugging, the result of t.String does include the monotonic clock reading if present. If t != u because of different monotonic clock readings, that difference will be visible when printing t.String() and u.String().

Timer Resolution

Timer resolution varies depending on the Go runtime, the operating system and the underlying hardware. On Unix, the resolution is ~1ms. On Windows version 1803 and newer, the resolution is ~0.5ms. On older Windows versions, the default resolution is ~16ms, but a higher resolution may be requested using golang.org/x/sys/windows.TimeBeginPeriod.

Index

Examples

Constants

View Source 
const (
	Layout      = "01/02 03:04:05PM '06 -0700" // The reference time, in numerical order.
	ANSIC       = "Mon Jan _2 15:04:05 2006"
	UnixDate    = "Mon Jan _2 15:04:05 MST 2006"
	RubyDate    = "Mon Jan 02 15:04:05 -0700 2006"
	RFC822      = "02 Jan 06 15:04 MST"
	RFC822Z     = "02 Jan 06 15:04 -0700" // RFC822 with numeric zone
	RFC850      = "Monday, 02-Jan-06 15:04:05 MST"
	RFC1123     = "Mon, 02 Jan 2006 15:04:05 MST"
	RFC1123Z    = "Mon, 02 Jan 2006 15:04:05 -0700" // RFC1123 with numeric zone
	RFC3339     = "2006-01-02T15:04:05Z07:00"
	RFC3339Nano = "2006-01-02T15:04:05.999999999Z07:00"
	Kitchen     = "3:04PM"
	// Handy time stamps.
	Stamp      = "Jan _2 15:04:05"
	StampMilli = "Jan _2 15:04:05.000"
	StampMicro = "Jan _2 15:04:05.000000"
	StampNano  = "Jan _2 15:04:05.000000000"
	DateTime   = "2006-01-02 15:04:05"
	DateOnly   = "2006-01-02"
	TimeOnly   = "15:04:05"
)

These are predefined layouts for use in Time.Format and time.Parse. The reference time used in these layouts is the specific time stamp: 

01/02 03:04:05PM '06 -0700

(January 2, 15:04:05, 2006, in time zone seven hours west of GMT). That value is recorded as the constant named Layout, listed below. As a Unix time, this is 1136239445. Since MST is GMT-0700, the reference would be printed by the Unix date command as: 

Mon Jan 2 15:04:05 MST 2006

It is a regrettable historic error that the date uses the American convention of putting the numerical month before the day.

The example for Time.Format demonstrates the working of the layout string in detail and is a good reference.

Note that the RFC822, RFC850, and RFC1123 formats should be applied only to local times. Applying them to UTC times will use "UTC" as the time zone abbreviation, while strictly speaking those RFCs require the use of "GMT" in that case. When using the RFC1123 or RFC1123Z formats for parsing, note that these formats define a leading zero for the day-in-month portion, which is not strictly allowed by RFC 1123. This will result in an error when parsing date strings that occur in the first 9 days of a given month. In general RFC1123Z should be used instead of RFC1123 for servers that insist on that format, and RFC3339 should be preferred for new protocols. RFC3339, RFC822, RFC822Z, RFC1123, and RFC1123Z are useful for formatting; when used with time.Parse they do not accept all the time formats permitted by the RFCs and they do accept time formats not formally defined. The RFC3339Nano format removes trailing zeros from the seconds field and thus may not sort correctly once formatted.

Most programs can use one of the defined constants as the layout passed to Format or Parse. The rest of this comment can be ignored unless you are creating a custom layout string.

To define your own format, write down what the reference time would look like formatted your way; see the values of constants like ANSIC, StampMicro or Kitchen for examples. The model is to demonstrate what the reference time looks like so that the Format and Parse methods can apply the same transformation to a general time value.

Here is a summary of the components of a layout string. Each element shows by example the formatting of an element of the reference time. Only these values are recognized. Text in the layout string that is not recognized as part of the reference time is echoed verbatim during Format and expected to appear verbatim in the input to Parse. 

Year: "2006" "06"
Month: "Jan" "January" "01" "1"
Day of the week: "Mon" "Monday"
Day of the month: "2" "_2" "02"
Day of the year: "__2" "002"
Hour: "15" "3" "03" (PM or AM)
Minute: "4" "04"
Second: "5" "05"
AM/PM mark: "PM"

Numeric time zone offsets format as follows: 

"-0700"     ±hhmm
"-07:00"    ±hh:mm
"-07"       ±hh
"-070000"   ±hhmmss
"-07:00:00" ±hh:mm:ss

Replacing the sign in the format with a Z triggers the ISO 8601 behavior of printing Z instead of an offset for the UTC zone. Thus: 

"Z0700"      Z or ±hhmm
"Z07:00"     Z or ±hh:mm
"Z07"        Z or ±hh
"Z070000"    Z or ±hhmmss
"Z07:00:00"  Z or ±hh:mm:ss

Within the format string, the underscores in "_2" and "__2" represent spaces that may be replaced by digits if the following number has multiple digits, for compatibility with fixed-width Unix time formats. A leading zero represents a zero-padded value.

The formats __2 and 002 are space-padded and zero-padded three-character day of year; there is no unpadded day of year format.

A comma or decimal point followed by one or more zeros represents a fractional second, printed to the given number of decimal places. A comma or decimal point followed by one or more nines represents a fractional second, printed to the given number of decimal places, with trailing zeros removed. For example "15:04:05,000" or "15:04:05.000" formats or parses with millisecond precision.

Some valid layouts are invalid time values for time.Parse, due to formats such as _ for space padding and Z for zone information.

View Source 
const (
	Nanosecond  Duration = 1
	Microsecond          = 1000 * Nanosecond
	Millisecond          = 1000 * Microsecond
	Second               = 1000 * Millisecond
	Minute               = 60 * Second
	Hour                 = 60 * Minute
)

Common durations. There is no definition for units of Day or larger to avoid confusion across daylight savings time zone transitions.

To count the number of units in a Duration, divide: 

second := time.Second
fmt.Print(int64(second/time.Millisecond)) // prints 1000

To convert an integer number of units to a Duration, multiply: 

seconds := 10
fmt.Print(time.Duration(seconds)*time.Second) // prints 10s

Variables

This section is empty.

Functions

func After 

func After(d Duration) <-chan Time

After waits for the duration to elapse and then sends the current time on the returned channel. It is equivalent to NewTimer(d).C.

Before Go 1.23, this documentation warned that the underlying Timer would not be recovered by the garbage collector until the timer fired, and that if efficiency was a concern, code should use NewTimer instead and call Timer.Stop if the timer is no longer needed. As of Go 1.23, the garbage collector can recover unreferenced, unstopped timers. There is no reason to prefer NewTimer when After will do.

Example 
package main

import (
	"fmt"
	"time"
)

var c chan int

func handle(int) {}

func main() {
	select {
	case m := <-c:
		handle(m)
	case <-time.After(10 * time.Second):
		fmt.Println("timed out")
	}
}

Output:

func Sleep 

func Sleep(d Duration)

Sleep pauses the current goroutine for at least the duration d. A negative or zero duration causes Sleep to return immediately.

Example 
package main

import (
	"time"
)

func main() {
	time.Sleep(100 * time.Millisecond)
}

Output:

func Tick 

func Tick(d Duration) <-chan Time

Tick is a convenience wrapper for NewTicker providing access to the ticking channel only. Unlike NewTicker, Tick will return nil if d <= 0.

Before Go 1.23, this documentation warned that the underlying Ticker would never be recovered by the garbage collector, and that if efficiency was a concern, code should use NewTicker instead and call Ticker.Stop when the ticker is no longer needed. As of Go 1.23, the garbage collector can recover unreferenced tickers, even if they haven't been stopped. The Stop method is no longer necessary to help the garbage collector. There is no longer any reason to prefer NewTicker when Tick will do.

Example 
package main

import (
	"fmt"
	"time"
)

func statusUpdate() string { return "" }

func main() {
	c := time.Tick(5 * time.Second)
	for next := range c {
		fmt.Printf("%v %s\n", next, statusUpdate())
	}
}

Output:

Types

type Duration 

type Duration int64

A Duration represents the elapsed time between two instants as an int64 nanosecond count. The representation limits the largest representable duration to approximately 290 years.

Example 
package main

import (
	"fmt"
	"time"
)

func expensiveCall() {}

func main() {
	t0 := time.Now()
	expensiveCall()
	t1 := time.Now()
	fmt.Printf("The call took %v to run.\n", t1.Sub(t0))
}

Output:

func ParseDuration 

func ParseDuration(s string) (Duration, error)

ParseDuration parses a duration string. A duration string is a possibly signed sequence of decimal numbers, each with optional fraction and a unit suffix, such as "300ms", "-1.5h" or "2h45m". Valid time units are "ns", "us" (or "µs"), "ms", "s", "m", "h".

Example 
package main

import (
	"fmt"
	"time"
)

func main() {
	hours, _ := time.ParseDuration("10h")
	complex, _ := time.ParseDuration("1h10m10s")
	micro, _ := time.ParseDuration("1µs")
	// The package also accepts the incorrect but common prefix u for micro.
	micro2, _ := time.ParseDuration("1us")

	fmt.Println(hours)
	fmt.Println(complex)
	fmt.Printf("There are %.0f seconds in %v.\n", complex.Seconds(), complex)
	fmt.Printf("There are %d nanoseconds in %v.\n", micro.Nanoseconds(), micro)
	fmt.Printf("There are %6.2e seconds in %v.\n", micro2.Seconds(), micro2)
}

Output:

10h0m0s
1h10m10s
There are 4210 seconds in 1h10m10s.
There are 1000 nanoseconds in 1µs.
There are 1.00e-06 seconds in 1µs.

func Since 

func Since(t Time) Duration

Since returns the time elapsed since t. It is shorthand for time.Now().Sub(t).

func Until added in go1.8 

func Until(t Time) Duration

Until returns the duration until t. It is shorthand for t.Sub(time.Now()).

func (Duration) Abs added in go1.19 

func (d Duration) Abs() Duration

Abs returns the absolute value of d. As a special case, math.MinInt64 is converted to math.MaxInt64.

func (Duration) Hours 

func (d Duration) Hours() float64

Hours returns the duration as a floating point number of hours.

Example 
package main

import (
	"fmt"
	"time"
)

func main() {
	h, _ := time.ParseDuration("4h30m")
	fmt.Printf("I've got %.1f hours of work left.", h.Hours())
}

Output:

I've got 4.5 hours of work left.

func (Duration) Microseconds added in go1.13 

func (d Duration) Microseconds() int64

Microseconds returns the duration as an integer microsecond count.

Example 
package main

import (
	"fmt"
	"time"
)

func main() {
	u, _ := time.ParseDuration("1s")
	fmt.Printf("One second is %d microseconds.\n", u.Microseconds())
}

Output:

One second is 1000000 microseconds.

func (Duration) Milliseconds added in go1.13 

func (d Duration) Milliseconds() int64

Milliseconds returns the duration as an integer millisecond count.

Example 
package main

import (
	"fmt"
	"time"
)

func main() {
	u, _ := time.ParseDuration("1s")
	fmt.Printf("One second is %d milliseconds.\n", u.Milliseconds())
}

Output:

One second is 1000 milliseconds.

func (Duration) Minutes 

func (d Duration) Minutes() float64

Minutes returns the duration as a floating point number of minutes.

Example 
package main

import (
	"fmt"
	"time"
)

func main() {
	m, _ := time.ParseDuration("1h30m")
	fmt.Printf("The movie is %.0f minutes long.", m.Minutes())
}

Output:

The movie is 90 minutes long.

func (Duration) Nanoseconds 

func (d Duration) Nanoseconds() int64

Nanoseconds returns the duration as an integer nanosecond count.

Example 
package main

import (
	"fmt"
	"time"
)

func main() {
	u, _ := time.ParseDuration("1µs")
	fmt.Printf("One microsecond is %d nanoseconds.\n", u.Nanoseconds())
}

Output:

One microsecond is 1000 nanoseconds.

func (Duration) Round added in go1.9 

func (d Duration) Round(m Duration) Duration

Round returns the result of rounding d to the nearest multiple of m. The rounding behavior for halfway values is to round away from zero. If the result exceeds the maximum (or minimum) value that can be stored in a Duration, Round returns the maximum (or minimum) duration. If m <= 0, Round returns d unchanged.

Example 
package main

import (
	"fmt"
	"time"
)

func main() {
	d, err := time.ParseDuration("1h15m30.918273645s")
	if err != nil {
		panic(err)
	}

	round := []time.Duration{
		time.Nanosecond,
		time.Microsecond,
		time.Millisecond,
		time.Second,
		2 * time.Second,
		time.Minute,
		10 * time.Minute,
		time.Hour,
	}

	for _, r := range round {
		fmt.Printf("d.Round(%6s) = %s\n", r, d.Round(r).String())
	}
}

Output:

d.Round(   1ns) = 1h15m30.918273645s
d.Round(   1µs) = 1h15m30.918274s
d.Round(   1ms) = 1h15m30.918s
d.Round(    1s) = 1h15m31s
d.Round(    2s) = 1h15m30s
d.Round(  1m0s) = 1h16m0s
d.Round( 10m0s) = 1h20m0s
d.Round(1h0m0s) = 1h0m0s

func (Duration) Seconds 

func (d Duration) Seconds() float64

Seconds returns the duration as a floating point number of seconds.

Example 
package main

import (
	"fmt"
	"time"
)

func main() {
	m, _ := time.ParseDuration("1m30s")
	fmt.Printf("Take off in t-%.0f seconds.", m.Seconds())
}

Output:

Take off in t-90 seconds.

func (Duration) String 

func (d Duration) String() string

String returns a string representing the duration in the form "72h3m0.5s". Leading zero units are omitted. As a special case, durations less than one second format use a smaller unit (milli-, micro-, or nanoseconds) to ensure that the leading digit is non-zero. The zero duration formats as 0s.

Example 
package main

import (
	"fmt"
	"time"
)

func main() {
	fmt.Println(1*time.Hour + 2*time.Minute + 300*time.Millisecond)
	fmt.Println(300 * time.Millisecond)
}

Output:

1h2m0.3s
300ms

func (Duration) Truncate added in go1.9 

func (d Duration) Truncate(m Duration) Duration

Truncate returns the result of rounding d toward zero to a multiple of m. If m <= 0, Truncate returns d unchanged.

Example 
package main

import (
	"fmt"
	"time"
)

func main() {
	d, err := time.ParseDuration("1h15m30.918273645s")
	if err != nil {
		panic(err)
	}

	trunc := []time.Duration{
		time.Nanosecond,
		time.Microsecond,
		time.Millisecond,
		time.Second,
		2 * time.Second,
		time.Minute,
		10 * time.Minute,
		time.Hour,
	}

	for _, t := range trunc {
		fmt.Printf("d.Truncate(%6s) = %s\n", t, d.Truncate(t).String())
	}
}

Output:

d.Truncate(   1ns) = 1h15m30.918273645s
d.Truncate(   1µs) = 1h15m30.918273s
d.Truncate(   1ms) = 1h15m30.918s
d.Truncate(    1s) = 1h15m30s
d.Truncate(    2s) = 1h15m30s
d.Truncate(  1m0s) = 1h15m0s
d.Truncate( 10m0s) = 1h10m0s
d.Truncate(1h0m0s) = 1h0m0s

type Location 

type Location struct {
	// contains filtered or unexported fields
}

A Location maps time instants to the zone in use at that time. Typically, the Location represents the collection of time offsets in use in a geographical area. For many Locations the time offset varies depending on whether daylight savings time is in use at the time instant.

Location is used to provide a time zone in a printed Time value and for calculations involving intervals that may cross daylight savings time boundaries.

Example 
package main

import (
	"fmt"
	"time"
)

func main() {
	// China doesn't have daylight saving. It uses a fixed 8 hour offset from UTC.
	secondsEastOfUTC := int((8 * time.Hour).Seconds())
	beijing := time.FixedZone("Beijing Time", secondsEastOfUTC)

	// If the system has a timezone database present, it's possible to load a location
	// from that, e.g.:
	//    newYork, err := time.LoadLocation("America/New_York")

	// Creating a time requires a location. Common locations are time.Local and time.UTC.
	timeInUTC := time.Date(2009, 1, 1, 12, 0, 0, 0, time.UTC)
	sameTimeInBeijing := time.Date(2009, 1, 1, 20, 0, 0, 0, beijing)

	// Although the UTC clock time is 1200 and the Beijing clock time is 2000, Beijing is
	// 8 hours ahead so the two dates actually represent the same instant.
	timesAreEqual := timeInUTC.Equal(sameTimeInBeijing)
	fmt.Println(timesAreEqual)

}

Output:

true

var Local *Location = &localLoc

Local represents the system's local time zone. On Unix systems, Local consults the TZ environment variable to find the time zone to use. No TZ means use the system default /etc/localtime. TZ="" means use UTC. TZ="foo" means use file foo in the system timezone directory. 

var UTC *Location = &utcLoc

UTC represents Universal Coordinated Time (UTC).

func FixedZone 

func FixedZone(name string, offset int) *Location

FixedZone returns a Location that always uses the given zone name and offset (seconds east of UTC).

Example 
package main

import (
	"fmt"
	"time"
)

func main() {
	loc := time.FixedZone("UTC-8", -8*60*60)
	t := time.Date(2009, time.November, 10, 23, 0, 0, 0, loc)
	fmt.Println("The time is:", t.Format(time.RFC822))
}

Output:

The time is: 10 Nov 09 23:00 UTC-8

func LoadLocation 

func LoadLocation(name string) (*Location, error)

LoadLocation returns the Location with the given name.

If the name is "" or "UTC", LoadLocation returns UTC. If the name is "Local", LoadLocation returns Local.

Otherwise, the name is taken to be a location name corresponding to a file in the IANA Time Zone database, such as "America/New_York".

LoadLocation looks for the IANA Time Zone database in the following locations in order:

  • the directory or uncompressed zip file named by the ZONEINFO environment variable
  • on a Unix system, the system standard installation location
  • $GOROOT/lib/time/zoneinfo.zip
  • the time/tzdata package, if it was imported
Example 
package main

import (
	"fmt"
	"time"
)

func main() {
	location, err := time.LoadLocation("America/Los_Angeles")
	if err != nil {
		panic(err)
	}

	timeInUTC := time.Date(2018, 8, 30, 12, 0, 0, 0, time.UTC)
	fmt.Println(timeInUTC.In(location))
}

Output:

2018-08-30 05:00:00 -0700 PDT

func LoadLocationFromTZData added in go1.10 

func LoadLocationFromTZData(name string, data []byte) (*Location, error)

LoadLocationFromTZData returns a Location with the given name initialized from the IANA Time Zone database-formatted data. The data should be in the format of a standard IANA time zone file (for example, the content of /etc/localtime on Unix systems).

func (*Location) String 

func (l *Location) String() string

String returns a descriptive name for the time zone information, corresponding to the name argument to LoadLocation or FixedZone.

type Month 

type Month int

A Month specifies a month of the year (January = 1, ...).

Example 
package main

import (
	"fmt"
	"time"
)

func main() {
	_, month, day := time.Now().Date()
	if month == time.November && day == 10 {
		fmt.Println("Happy Go day!")
	}
}

Output:


const (
	January Month = 1 + iota
	February
	March
	April
	May
	June
	July
	August
	September
	October
	November
	December
)

func (Month) String 

func (m Month) String() string

String returns the English name of the month ("January", "February", ...).

type ParseError 

type ParseError struct {
	Layout     string
	Value      string
	LayoutElem string
	ValueElem  string
	Message    string
}

ParseError describes a problem parsing a time string.

func (*ParseError) Error 

func (e *ParseError) Error() string

Error returns the string representation of a ParseError.

type Ticker 

type Ticker struct {
	C <-chan Time // The channel on which the ticks are delivered.
	// contains filtered or unexported fields
}

A Ticker holds a channel that delivers “ticks” of a clock at intervals.

func NewTicker 

func NewTicker(d Duration) *Ticker

NewTicker returns a new Ticker containing a channel that will send the current time on the channel after each tick. The period of the ticks is specified by the duration argument. The ticker will adjust the time interval or drop ticks to make up for slow receivers. The duration d must be greater than zero; if not, NewTicker will panic.

Before Go 1.23, the garbage collector did not recover tickers that had not yet expired or been stopped, so code often immediately deferred t.Stop after calling NewTicker, to make the ticker recoverable when it was no longer needed. As of Go 1.23, the garbage collector can recover unreferenced tickers, even if they haven't been stopped. The Stop method is no longer necessary to help the garbage collector. (Code may of course still want to call Stop to stop the ticker for other reasons.)

Example 
package main

import (
	"fmt"
	"time"
)

func main() {
	ticker := time.NewTicker(time.Second)
	defer ticker.Stop()
	done := make(chan bool)
	go func() {
		time.Sleep(10 * time.Second)
		done <- true
	}()
	for {
		select {
		case <-done:
			fmt.Println("Done!")
			return
		case t := <-ticker.C:
			fmt.Println("Current time: ", t)
		}
	}
}

Output:

func (*Ticker) Reset added in go1.15 

func (t *Ticker) Reset(d Duration)

Reset stops a ticker and resets its period to the specified duration. The next tick will arrive after the new period elapses. The duration d must be greater than zero; if not, Reset will panic.

func (*Ticker) Stop 

func (t *Ticker) Stop()

Stop turns off a ticker. After Stop, no more ticks will be sent. Stop does not close the channel, to prevent a concurrent goroutine reading from the channel from seeing an erroneous "tick".

type Time 

type Time struct {
	// contains filtered or unexported fields
}

A Time represents an instant in time with nanosecond precision.

Programs using times should typically store and pass them as values, not pointers. That is, time variables and struct fields should be of type time.Time, not *time.Time.

A Time value can be used by multiple goroutines simultaneously except that the methods Time.GobDecode, Time.UnmarshalBinary, Time.UnmarshalJSON and Time.UnmarshalText are not concurrency-safe.

Time instants can be compared using the Time.Before, Time.After, and Time.Equal methods. The Time.Sub method subtracts two instants, producing a Duration. The Time.Add method adds a Time and a Duration, producing a Time.

The zero value of type Time is January 1, year 1, 00:00:00.000000000 UTC. As this time is unlikely to come up in practice, the Time.IsZero method gives a simple way of detecting a time that has not been initialized explicitly.

Each time has an associated Location. The methods Time.Local, Time.UTC, and Time.In return a Time with a specific Location. Changing the Location of a Time value with these methods does not change the actual instant it represents, only the time zone in which to interpret it.

Representations of a Time value saved by the Time.GobEncode, Time.MarshalBinary, Time.MarshalJSON, and Time.MarshalText methods store the Time.Location's offset, but not the location name. They therefore lose information about Daylight Saving Time.

In addition to the required “wall clock” reading, a Time may contain an optional reading of the current process's monotonic clock, to provide additional precision for comparison or subtraction. See the “Monotonic Clocks” section in the package documentation for details.

Note that the Go == operator compares not just the time instant but also the Location and the monotonic clock reading. Therefore, Time values should not be used as map or database keys without first guaranteeing that the identical Location has been set for all values, which can be achieved through use of the UTC or Local method, and that the monotonic clock reading has been stripped by setting t = t.Round(0). In general, prefer t.Equal(u) to t == u, since t.Equal uses the most accurate comparison available and correctly handles the case when only one of its arguments has a monotonic clock reading.

func Date 

func Date(year int, month Month, day, hour, min, sec, nsec int, loc *Location) Time

Date returns the Time corresponding to 

yyyy-mm-dd hh:mm:ss + nsec nanoseconds

in the appropriate zone for that time in the given location.

The month, day, hour, min, sec, and nsec values may be outside their usual ranges and will be normalized during the conversion. For example, October 32 converts to November 1.

A daylight savings time transition skips or repeats times. For example, in the United States, March 13, 2011 2:15am never occurred, while November 6, 2011 1:15am occurred twice. In such cases, the choice of time zone, and therefore the time, is not well-defined. Date returns a time that is correct in one of the two zones involved in the transition, but it does not guarantee which.

Date panics if loc is nil.

Example 
package main

import (
	"fmt"
	"time"
)

func main() {
	t := time.Date(2009, time.November, 10, 23, 0, 0, 0, time.UTC)
	fmt.Printf("Go launched at %s\n", t.Local())
}

Output:

Go launched at 2009-11-10 15:00:00 -0800 PST

func Now 

func Now() Time

Now returns the current local time.

func Parse 

func Parse(layout, value string) (Time, error)

Parse parses a formatted string and returns the time value it represents. See the documentation for the constant called Layout to see how to represent the format. The second argument must be parseable using the format string (layout) provided as the first argument.

The example for Time.Format demonstrates the working of the layout string in detail and is a good reference.

When parsing (only), the input may contain a fractional second field immediately after the seconds field, even if the layout does not signify its presence. In that case either a comma or a decimal point followed by a maximal series of digits is parsed as a fractional second. Fractional seconds are truncated to nanosecond precision.

Elements omitted from the layout are assumed to be zero or, when zero is impossible, one, so parsing "3:04pm" returns the time corresponding to Jan 1, year 0, 15:04:00 UTC (note that because the year is 0, this time is before the zero Time). Years must be in the range 0000..9999. The day of the week is checked for syntax but it is otherwise ignored.

For layouts specifying the two-digit year 06, a value NN >= 69 will be treated as 19NN and a value NN < 69 will be treated as 20NN.

The remainder of this comment describes the handling of time zones.

In the absence of a time zone indicator, Parse returns a time in UTC.

When parsing a time with a zone offset like -0700, if the offset corresponds to a time zone used by the current location (Local), then Parse uses that location and zone in the returned time. Otherwise it records the time as being in a fabricated location with time fixed at the given zone offset.

When parsing a time with a zone abbreviation like MST, if the zone abbreviation has a defined offset in the current location, then that offset is used. The zone abbreviation "UTC" is recognized as UTC regardless of location. If the zone abbreviation is unknown, Parse records the time as being in a fabricated location with the given zone abbreviation and a zero offset. This choice means that such a time can be parsed and reformatted with the same layout losslessly, but the exact instant used in the representation will differ by the actual zone offset. To avoid such problems, prefer time layouts that use a numeric zone offset, or use ParseInLocation.

Example 
package main

import (
	"fmt"
	"time"
)

func main() {
	// See the example for Time.Format for a thorough description of how
	// to define the layout string to parse a time.Time value; Parse and
	// Format use the same model to describe their input and output.

	// longForm shows by example how the reference time would be represented in
	// the desired layout.
	const longForm = "Jan 2, 2006 at 3:04pm (MST)"
	t, _ := time.Parse(longForm, "Feb 3, 2013 at 7:54pm (PST)")
	fmt.Println(t)

	// shortForm is another way the reference time would be represented
	// in the desired layout; it has no time zone present.
	// Note: without explicit zone, returns time in UTC.
	const shortForm = "2006-Jan-02"
	t, _ = time.Parse(shortForm, "2013-Feb-03")
	fmt.Println(t)

	// Some valid layouts are invalid time values, due to format specifiers
	// such as _ for space padding and Z for zone information.
	// For example the RFC3339 layout 2006-01-02T15:04:05Z07:00
	// contains both Z and a time zone offset in order to handle both valid options:
	// 2006-01-02T15:04:05Z
	// 2006-01-02T15:04:05+07:00
	t, _ = time.Parse(time.RFC3339, "2006-01-02T15:04:05Z")
	fmt.Println(t)
	t, _ = time.Parse(time.RFC3339, "2006-01-02T15:04:05+07:00")
	fmt.Println(t)
	_, err := time.Parse(time.RFC3339, time.RFC3339)
	fmt.Println("error", err) // Returns an error as the layout is not a valid time value

}

Output:

2013-02-03 19:54:00 -0800 PST
2013-02-03 00:00:00 +0000 UTC
2006-01-02 15:04:05 +0000 UTC
2006-01-02 15:04:05 +0700 +0700
error parsing time "2006-01-02T15:04:05Z07:00": extra text: "07:00"

func ParseInLocation added in go1.1 

func ParseInLocation(layout, value string, loc *Location) (Time, error)

ParseInLocation is like Parse but differs in two important ways. First, in the absence of time zone information, Parse interprets a time as UTC; ParseInLocation interprets the time as in the given location. Second, when given a zone offset or abbreviation, Parse tries to match it against the Local location; ParseInLocation uses the given location.

Example 
package main

import (
	"fmt"
	"time"
)

func main() {
	loc, _ := time.LoadLocation("Europe/Berlin")

	// This will look for the name CEST in the Europe/Berlin time zone.
	const longForm = "Jan 2, 2006 at 3:04pm (MST)"
	t, _ := time.ParseInLocation(longForm, "Jul 9, 2012 at 5:02am (CEST)", loc)
	fmt.Println(t)

	// Note: without explicit zone, returns time in given location.
	const shortForm = "2006-Jan-02"
	t, _ = time.ParseInLocation(shortForm, "2012-Jul-09", loc)
	fmt.Println(t)

}

Output:

2012-07-09 05:02:00 +0200 CEST
2012-07-09 00:00:00 +0200 CEST

func Unix 

func Unix(sec int64, nsec int64) Time

Unix returns the local Time corresponding to the given Unix time, sec seconds and nsec nanoseconds since January 1, 1970 UTC. It is valid to pass nsec outside the range [0, 999999999]. Not all sec values have a corresponding time value. One such value is 1<<63-1 (the largest int64 value).

Example 
package main

import (
	"fmt"
	"time"
)

func main() {
	unixTime := time.Date(2009, time.November, 10, 23, 0, 0, 0, time.UTC)
	fmt.Println(unixTime.Unix())
	t := time.Unix(unixTime.Unix(), 0).UTC()
	fmt.Println(t)

}

Output:

1257894000
2009-11-10 23:00:00 +0000 UTC

func UnixMicro added in go1.17 

func UnixMicro(usec int64) Time

UnixMicro returns the local Time corresponding to the given Unix time, usec microseconds since January 1, 1970 UTC.

Example 
package main

import (
	"fmt"
	"time"
)

func main() {
	umt := time.Date(2009, time.November, 10, 23, 0, 0, 0, time.UTC)
	fmt.Println(umt.UnixMicro())
	t := time.UnixMicro(umt.UnixMicro()).UTC()
	fmt.Println(t)

}

Output:

1257894000000000
2009-11-10 23:00:00 +0000 UTC

func UnixMilli added in go1.17 

func UnixMilli(msec int64) Time

UnixMilli returns the local Time corresponding to the given Unix time, msec milliseconds since January 1, 1970 UTC.

Example 
package main

import (
	"fmt"
	"time"
)

func main() {
	umt := time.Date(2009, time.November, 10, 23, 0, 0, 0, time.UTC)
	fmt.Println(umt.UnixMilli())
	t := time.UnixMilli(umt.UnixMilli()).UTC()
	fmt.Println(t)

}

Output:

1257894000000
2009-11-10 23:00:00 +0000 UTC

func (Time) Add 

func (t Time) Add(d Duration) Time

Add returns the time t+d.

Example 
package main

import (
	"fmt"
	"time"
)

func main() {
	start := time.Date(2009, 1, 1, 12, 0, 0, 0, time.UTC)
	afterTenSeconds := start.Add(time.Second * 10)
	afterTenMinutes := start.Add(time.Minute * 10)
	afterTenHours := start.Add(time.Hour * 10)
	afterTenDays := start.Add(time.Hour * 24 * 10)

	fmt.Printf("start = %v\n", start)
	fmt.Printf("start.Add(time.Second * 10) = %v\n", afterTenSeconds)
	fmt.Printf("start.Add(time.Minute * 10) = %v\n", afterTenMinutes)
	fmt.Printf("start.Add(time.Hour * 10) = %v\n", afterTenHours)
	fmt.Printf("start.Add(time.Hour * 24 * 10) = %v\n", afterTenDays)

}

Output:

start = 2009-01-01 12:00:00 +0000 UTC
start.Add(time.Second * 10) = 2009-01-01 12:00:10 +0000 UTC
start.Add(time.Minute * 10) = 2009-01-01 12:10:00 +0000 UTC
start.Add(time.Hour * 10) = 2009-01-01 22:00:00 +0000 UTC
start.Add(time.Hour * 24 * 10) = 2009-01-11 12:00:00 +0000 UTC

func (Time) AddDate 

func (t Time) AddDate(years int, months int, days int) Time

AddDate returns the time corresponding to adding the given number of years, months, and days to t. For example, AddDate(-1, 2, 3) applied to January 1, 2011 returns March 4, 2010.

Note that dates are fundamentally coupled to timezones, and calendrical periods like days don't have fixed durations. AddDate uses the Location of the Time value to determine these durations. That means that the same AddDate arguments can produce a different shift in absolute time depending on the base Time value and its Location. For example, AddDate(0, 0, 1) applied to 12:00 on March 27 always returns 12:00 on March 28. At some locations and in some years this is a 24 hour shift. In others it's a 23 hour shift due to daylight savings time transitions.

AddDate normalizes its result in the same way that Date does, so, for example, adding one month to October 31 yields December 1, the normalized form for November 31.

Example 
package main

import (
	"fmt"
	"time"
)

func main() {
	start := time.Date(2023, 03, 25, 12, 0, 0, 0, time.UTC)
	oneDayLater := start.AddDate(0, 0, 1)
	dayDuration := oneDayLater.Sub(start)
	oneMonthLater := start.AddDate(0, 1, 0)
	oneYearLater := start.AddDate(1, 0, 0)

	zurich, err := time.LoadLocation("Europe/Zurich")
	if err != nil {
		panic(err)
	}
	// This was the day before a daylight saving time transition in Zürich.
	startZurich := time.Date(2023, 03, 25, 12, 0, 0, 0, zurich)
	oneDayLaterZurich := startZurich.AddDate(0, 0, 1)
	dayDurationZurich := oneDayLaterZurich.Sub(startZurich)

	fmt.Printf("oneDayLater: start.AddDate(0, 0, 1) = %v\n", oneDayLater)
	fmt.Printf("oneMonthLater: start.AddDate(0, 1, 0) = %v\n", oneMonthLater)
	fmt.Printf("oneYearLater: start.AddDate(1, 0, 0) = %v\n", oneYearLater)
	fmt.Printf("oneDayLaterZurich: startZurich.AddDate(0, 0, 1) = %v\n", oneDayLaterZurich)
	fmt.Printf("Day duration in UTC: %v | Day duration in Zürich: %v\n", dayDuration, dayDurationZurich)

}

Output:

oneDayLater: start.AddDate(0, 0, 1) = 2023-03-26 12:00:00 +0000 UTC
oneMonthLater: start.AddDate(0, 1, 0) = 2023-04-25 12:00:00 +0000 UTC
oneYearLater: start.AddDate(1, 0, 0) = 2024-03-25 12:00:00 +0000 UTC
oneDayLaterZurich: startZurich.AddDate(0, 0, 1) = 2023-03-26 12:00:00 +0200 CEST
Day duration in UTC: 24h0m0s | Day duration in Zürich: 23h0m0s

func (Time) After 

func (t Time) After(u Time) bool

After reports whether the time instant t is after u.

Example 
package main

import (
	"fmt"
	"time"
)

func main() {
	year2000 := time.Date(2000, 1, 1, 0, 0, 0, 0, time.UTC)
	year3000 := time.Date(3000, 1, 1, 0, 0, 0, 0, time.UTC)

	isYear3000AfterYear2000 := year3000.After(year2000) // True
	isYear2000AfterYear3000 := year2000.After(year3000) // False

	fmt.Printf("year3000.After(year2000) = %v\n", isYear3000AfterYear2000)
	fmt.Printf("year2000.After(year3000) = %v\n", isYear2000AfterYear3000)

}

Output:

year3000.After(year2000) = true
year2000.After(year3000) = false

func (Time) AppendFormat added in go1.5 

func (t Time) AppendFormat(b []byte, layout string) []byte

AppendFormat is like Time.Format but appends the textual representation to b and returns the extended buffer.

Example 
package main

import (
	"fmt"
	"time"
)

func main() {
	t := time.Date(2017, time.November, 4, 11, 0, 0, 0, time.UTC)
	text := []byte("Time: ")

	text = t.AppendFormat(text, time.Kitchen)
	fmt.Println(string(text))

}

Output:

Time: 11:00AM

func (Time) Before 

func (t Time) Before(u Time) bool

Before reports whether the time instant t is before u.

Example 
package main

import (
	"fmt"
	"time"
)

func main() {
	year2000 := time.Date(2000, 1, 1, 0, 0, 0, 0, time.UTC)
	year3000 := time.Date(3000, 1, 1, 0, 0, 0, 0, time.UTC)

	isYear2000BeforeYear3000 := year2000.Before(year3000) // True
	isYear3000BeforeYear2000 := year3000.Before(year2000) // False

	fmt.Printf("year2000.Before(year3000) = %v\n", isYear2000BeforeYear3000)
	fmt.Printf("year3000.Before(year2000) = %v\n", isYear3000BeforeYear2000)

}

Output:

year2000.Before(year3000) = true
year3000.Before(year2000) = false

func (Time) Clock 

func (t Time) Clock() (hour, min, sec int)

Clock returns the hour, minute, and second within the day specified by t.

func (Time) Compare added in go1.20 

func (t Time) Compare(u Time) int

Compare compares the time instant t with u. If t is before u, it returns -1; if t is after u, it returns +1; if they're the same, it returns 0.

func (Time) Date 

func (t Time) Date() (year int, month Month, day int)

Date returns the year, month, and day in which t occurs.

Example 
package main

import (
	"fmt"
	"time"
)

func main() {
	d := time.Date(2000, 2, 1, 12, 30, 0, 0, time.UTC)
	year, month, day := d.Date()

	fmt.Printf("year = %v\n", year)
	fmt.Printf("month = %v\n", month)
	fmt.Printf("day = %v\n", day)

}

Output:

year = 2000
month = February
day = 1

func (Time) Day 

func (t Time) Day() int

Day returns the day of the month specified by t.

Example 
package main

import (
	"fmt"
	"time"
)

func main() {
	d := time.Date(2000, 2, 1, 12, 30, 0, 0, time.UTC)
	day := d.Day()

	fmt.Printf("day = %v\n", day)

}

Output:

day = 1

func (Time) Equal 

func (t Time) Equal(u Time) bool

Equal reports whether t and u represent the same time instant. Two times can be equal even if they are in different locations. For example, 6:00 +0200 and 4:00 UTC are Equal. See the documentation on the Time type for the pitfalls of using == with Time values; most code should use Equal instead.

Example 
package main

import (
	"fmt"
	"time"
)

func main() {
	secondsEastOfUTC := int((8 * time.Hour).Seconds())
	beijing := time.FixedZone("Beijing Time", secondsEastOfUTC)

	// Unlike the equal operator, Equal is aware that d1 and d2 are the
	// same instant but in different time zones.
	d1 := time.Date(2000, 2, 1, 12, 30, 0, 0, time.UTC)
	d2 := time.Date(2000, 2, 1, 20, 30, 0, 0, beijing)

	datesEqualUsingEqualOperator := d1 == d2
	datesEqualUsingFunction := d1.Equal(d2)

	fmt.Printf("datesEqualUsingEqualOperator = %v\n", datesEqualUsingEqualOperator)
	fmt.Printf("datesEqualUsingFunction = %v\n", datesEqualUsingFunction)

}

Output:

datesEqualUsingEqualOperator = false
datesEqualUsingFunction = true

func (Time) Format 

func (t Time) Format(layout string) string

Format returns a textual representation of the time value formatted according to the layout defined by the argument. See the documentation for the constant called Layout to see how to represent the layout format.

The executable example for Time.Format demonstrates the working of the layout string in detail and is a good reference.

Example 
package main

import (
	"fmt"
	"time"
)

func main() {
	// Parse a time value from a string in the standard Unix format.
	t, err := time.Parse(time.UnixDate, "Wed Feb 25 11:06:39 PST 2015")
	if err != nil { // Always check errors even if they should not happen.
		panic(err)
	}

	tz, err := time.LoadLocation("Asia/Shanghai")
	if err != nil { // Always check errors even if they should not happen.
		panic(err)
	}

	// time.Time's Stringer method is useful without any format.
	fmt.Println("default format:", t)

	// Predefined constants in the package implement common layouts.
	fmt.Println("Unix format:", t.Format(time.UnixDate))

	// The time zone attached to the time value affects its output.
	fmt.Println("Same, in UTC:", t.UTC().Format(time.UnixDate))

	fmt.Println("in Shanghai with seconds:", t.In(tz).Format("2006-01-02T15:04:05 -070000"))

	fmt.Println("in Shanghai with colon seconds:", t.In(tz).Format("2006-01-02T15:04:05 -07:00:00"))

	// The rest of this function demonstrates the properties of the
	// layout string used in the format.

	// The layout string used by the Parse function and Format method
	// shows by example how the reference time should be represented.
	// We stress that one must show how the reference time is formatted,
	// not a time of the user's choosing. Thus each layout string is a
	// representation of the time stamp,
	//	Jan 2 15:04:05 2006 MST
	// An easy way to remember this value is that it holds, when presented
	// in this order, the values (lined up with the elements above):
	//	  1 2  3  4  5    6  -7
	// There are some wrinkles illustrated below.

	// Most uses of Format and Parse use constant layout strings such as
	// the ones defined in this package, but the interface is flexible,
	// as these examples show.

	// Define a helper function to make the examples' output look nice.
	do := func(name, layout, want string) {
		got := t.Format(layout)
		if want != got {
			fmt.Printf("error: for %q got %q; expected %q\n", layout, got, want)
			return
		}
		fmt.Printf("%-16s %q gives %q\n", name, layout, got)
	}

	// Print a header in our output.
	fmt.Printf("\nFormats:\n\n")

	// Simple starter examples.
	do("Basic full date", "Mon Jan 2 15:04:05 MST 2006", "Wed Feb 25 11:06:39 PST 2015")
	do("Basic short date", "2006/01/02", "2015/02/25")

	// The hour of the reference time is 15, or 3PM. The layout can express
	// it either way, and since our value is the morning we should see it as
	// an AM time. We show both in one format string. Lower case too.
	do("AM/PM", "3PM==3pm==15h", "11AM==11am==11h")

	// When parsing, if the seconds value is followed by a decimal point
	// and some digits, that is taken as a fraction of a second even if
	// the layout string does not represent the fractional second.
	// Here we add a fractional second to our time value used above.
	t, err = time.Parse(time.UnixDate, "Wed Feb 25 11:06:39.1234 PST 2015")
	if err != nil {
		panic(err)
	}
	// It does not appear in the output if the layout string does not contain
	// a representation of the fractional second.
	do("No fraction", time.UnixDate, "Wed Feb 25 11:06:39 PST 2015")

	// Fractional seconds can be printed by adding a run of 0s or 9s after
	// a decimal point in the seconds value in the layout string.
	// If the layout digits are 0s, the fractional second is of the specified
	// width. Note that the output has a trailing zero.
	do("0s for fraction", "15:04:05.00000", "11:06:39.12340")

	// If the fraction in the layout is 9s, trailing zeros are dropped.
	do("9s for fraction", "15:04:05.99999999", "11:06:39.1234")

}

Output:

default format: 2015-02-25 11:06:39 -0800 PST
Unix format: Wed Feb 25 11:06:39 PST 2015
Same, in UTC: Wed Feb 25 19:06:39 UTC 2015
in Shanghai with seconds: 2015-02-26T03:06:39 +080000
in Shanghai with colon seconds: 2015-02-26T03:06:39 +08:00:00

Formats:

Basic full date  "Mon Jan 2 15:04:05 MST 2006" gives "Wed Feb 25 11:06:39 PST 2015"
Basic short date "2006/01/02" gives "2015/02/25"
AM/PM            "3PM==3pm==15h" gives "11AM==11am==11h"
No fraction      "Mon Jan _2 15:04:05 MST 2006" gives "Wed Feb 25 11:06:39 PST 2015"
0s for fraction  "15:04:05.00000" gives "11:06:39.12340"
9s for fraction  "15:04:05.99999999" gives "11:06:39.1234"
Example (Pad) 
package main

import (
	"fmt"
	"time"
)

func main() {
	// Parse a time value from a string in the standard Unix format.
	t, err := time.Parse(time.UnixDate, "Sat Mar 7 11:06:39 PST 2015")
	if err != nil { // Always check errors even if they should not happen.
		panic(err)
	}

	// Define a helper function to make the examples' output look nice.
	do := func(name, layout, want string) {
		got := t.Format(layout)
		if want != got {
			fmt.Printf("error: for %q got %q; expected %q\n", layout, got, want)
			return
		}
		fmt.Printf("%-16s %q gives %q\n", name, layout, got)
	}

	// The predefined constant Unix uses an underscore to pad the day.
	do("Unix", time.UnixDate, "Sat Mar  7 11:06:39 PST 2015")

	// For fixed-width printing of values, such as the date, that may be one or
	// two characters (7 vs. 07), use an _ instead of a space in the layout string.
	// Here we print just the day, which is 2 in our layout string and 7 in our
	// value.
	do("No pad", "<2>", "<7>")

	// An underscore represents a space pad, if the date only has one digit.
	do("Spaces", "<_2>", "< 7>")

	// A "0" indicates zero padding for single-digit values.
	do("Zeros", "<02>", "<07>")

	// If the value is already the right width, padding is not used.
	// For instance, the second (05 in the reference time) in our value is 39,
	// so it doesn't need padding, but the minutes (04, 06) does.
	do("Suppressed pad", "04:05", "06:39")

}

Output:

Unix             "Mon Jan _2 15:04:05 MST 2006" gives "Sat Mar  7 11:06:39 PST 2015"
No pad           "<2>" gives "<7>"
Spaces           "<_2>" gives "< 7>"
Zeros            "<02>" gives "<07>"
Suppressed pad   "04:05" gives "06:39"

func (Time) GoString added in go1.17 

func (t Time) GoString() string

GoString implements fmt.GoStringer and formats t to be printed in Go source code.

Example 
package main

import (
	"fmt"
	"time"
)

func main() {
	t := time.Date(2009, time.November, 10, 23, 0, 0, 0, time.UTC)
	fmt.Println(t.GoString())
	t = t.Add(1 * time.Minute)
	fmt.Println(t.GoString())
	t = t.AddDate(0, 1, 0)
	fmt.Println(t.GoString())
	t, _ = time.Parse("Jan 2, 2006 at 3:04pm (MST)", "Feb 3, 2013 at 7:54pm (UTC)")
	fmt.Println(t.GoString())

}

Output:

time.Date(2009, time.November, 10, 23, 0, 0, 0, time.UTC)
time.Date(2009, time.November, 10, 23, 1, 0, 0, time.UTC)
time.Date(2009, time.December, 10, 23, 1, 0, 0, time.UTC)
time.Date(2013, time.February, 3, 19, 54, 0, 0, time.UTC)

func (*Time) GobDecode 

func (t *Time) GobDecode(data []byte) error

GobDecode implements the gob.GobDecoder interface.

func (Time) GobEncode 

func (t Time) GobEncode() ([]byte, error)

GobEncode implements the gob.GobEncoder interface.

func (Time) Hour 

func (t Time) Hour() int

Hour returns the hour within the day specified by t, in the range [0, 23].

func (Time) ISOWeek 

func (t Time) ISOWeek() (year, week int)

ISOWeek returns the ISO 8601 year and week number in which t occurs. Week ranges from 1 to 53. Jan 01 to Jan 03 of year n might belong to week 52 or 53 of year n-1, and Dec 29 to Dec 31 might belong to week 1 of year n+1.

func (Time) In 

func (t Time) In(loc *Location) Time

In returns a copy of t representing the same time instant, but with the copy's location information set to loc for display purposes.

In panics if loc is nil.

func (Time) IsDST added in go1.17 

func (t Time) IsDST() bool

IsDST reports whether the time in the configured location is in Daylight Savings Time.

func (Time) IsZero 

func (t Time) IsZero() bool

IsZero reports whether t represents the zero time instant, January 1, year 1, 00:00:00 UTC.

func (Time) Local 

func (t Time) Local() Time

Local returns t with the location set to local time.

func (Time) Location 

func (t Time) Location() *Location

Location returns the time zone information associated with t.

func (Time) MarshalBinary added in go1.2 

func (t Time) MarshalBinary() ([]byte, error)

MarshalBinary implements the encoding.BinaryMarshaler interface.

func (Time) MarshalJSON 

func (t Time) MarshalJSON() ([]byte, error)

MarshalJSON implements the [json.Marshaler] interface. The time is a quoted string in the RFC 3339 format with sub-second precision. If the timestamp cannot be represented as valid RFC 3339 (e.g., the year is out of range), then an error is reported.

func (Time) MarshalText added in go1.2 

func (t Time) MarshalText() ([]byte, error)

MarshalText implements the encoding.TextMarshaler interface. The time is formatted in RFC 3339 format with sub-second precision. If the timestamp cannot be represented as valid RFC 3339 (e.g., the year is out of range), then an error is reported.

func (Time) Minute 

func (t Time) Minute() int

Minute returns the minute offset within the hour specified by t, in the range [0, 59].

func (Time) Month 

func (t Time) Month() Month

Month returns the month of the year specified by t.

func (Time) Nanosecond 

func (t Time) Nanosecond() int

Nanosecond returns the nanosecond offset within the second specified by t, in the range [0, 999999999].

func (Time) Round added in go1.1 

func (t Time) Round(d Duration) Time

Round returns the result of rounding t to the nearest multiple of d (since the zero time). The rounding behavior for halfway values is to round up. If d <= 0, Round returns t stripped of any monotonic clock reading but otherwise unchanged.

Round operates on the time as an absolute duration since the zero time; it does not operate on the presentation form of the time. Thus, Round(Hour) may return a time with a non-zero minute, depending on the time's Location.

Example 
package main

import (
	"fmt"
	"time"
)

func main() {
	t := time.Date(0, 0, 0, 12, 15, 30, 918273645, time.UTC)
	round := []time.Duration{
		time.Nanosecond,
		time.Microsecond,
		time.Millisecond,
		time.Second,
		2 * time.Second,
		time.Minute,
		10 * time.Minute,
		time.Hour,
	}

	for _, d := range round {
		fmt.Printf("t.Round(%6s) = %s\n", d, t.Round(d).Format("15:04:05.999999999"))
	}
}

Output:

t.Round(   1ns) = 12:15:30.918273645
t.Round(   1µs) = 12:15:30.918274
t.Round(   1ms) = 12:15:30.918
t.Round(    1s) = 12:15:31
t.Round(    2s) = 12:15:30
t.Round(  1m0s) = 12:16:00
t.Round( 10m0s) = 12:20:00
t.Round(1h0m0s) = 12:00:00

func (Time) Second 

func (t Time) Second() int

Second returns the second offset within the minute specified by t, in the range [0, 59].

func (Time) String 

func (t Time) String() string

String returns the time formatted using the format string 

"2006-01-02 15:04:05.999999999 -0700 MST"

If the time has a monotonic clock reading, the returned string includes a final field "m=±<value>", where value is the monotonic clock reading formatted as a decimal number of seconds.

The returned string is meant for debugging; for a stable serialized representation, use t.MarshalText, t.MarshalBinary, or t.Format with an explicit format string.

Example 
package main

import (
	"fmt"
	"time"
)

func main() {
	timeWithNanoseconds := time.Date(2000, 2, 1, 12, 13, 14, 15, time.UTC)
	withNanoseconds := timeWithNanoseconds.String()

	timeWithoutNanoseconds := time.Date(2000, 2, 1, 12, 13, 14, 0, time.UTC)
	withoutNanoseconds := timeWithoutNanoseconds.String()

	fmt.Printf("withNanoseconds = %v\n", string(withNanoseconds))
	fmt.Printf("withoutNanoseconds = %v\n", string(withoutNanoseconds))

}

Output:

withNanoseconds = 2000-02-01 12:13:14.000000015 +0000 UTC
withoutNanoseconds = 2000-02-01 12:13:14 +0000 UTC

func (Time) Sub 

func (t Time) Sub(u Time) Duration

Sub returns the duration t-u. If the result exceeds the maximum (or minimum) value that can be stored in a Duration, the maximum (or minimum) duration will be returned. To compute t-d for a duration d, use t.Add(-d).

Example 
package main

import (
	"fmt"
	"time"
)

func main() {
	start := time.Date(2000, 1, 1, 0, 0, 0, 0, time.UTC)
	end := time.Date(2000, 1, 1, 12, 0, 0, 0, time.UTC)

	difference := end.Sub(start)
	fmt.Printf("difference = %v\n", difference)

}

Output:

difference = 12h0m0s

func (Time) Truncate added in go1.1 

func (t Time) Truncate(d Duration) Time

Truncate returns the result of rounding t down to a multiple of d (since the zero time). If d <= 0, Truncate returns t stripped of any monotonic clock reading but otherwise unchanged.

Truncate operates on the time as an absolute duration since the zero time; it does not operate on the presentation form of the time. Thus, Truncate(Hour) may return a time with a non-zero minute, depending on the time's Location.

Example 
package main

import (
	"fmt"
	"time"
)

func main() {
	t, _ := time.Parse("2006 Jan 02 15:04:05", "2012 Dec 07 12:15:30.918273645")
	trunc := []time.Duration{
		time.Nanosecond,
		time.Microsecond,
		time.Millisecond,
		time.Second,
		2 * time.Second,
		time.Minute,
		10 * time.Minute,
	}

	for _, d := range trunc {
		fmt.Printf("t.Truncate(%5s) = %s\n", d, t.Truncate(d).Format("15:04:05.999999999"))
	}
	// To round to the last midnight in the local timezone, create a new Date.
	midnight := time.Date(t.Year(), t.Month(), t.Day(), 0, 0, 0, 0, time.Local)
	_ = midnight

}

Output:

t.Truncate(  1ns) = 12:15:30.918273645
t.Truncate(  1µs) = 12:15:30.918273
t.Truncate(  1ms) = 12:15:30.918
t.Truncate(   1s) = 12:15:30
t.Truncate(   2s) = 12:15:30
t.Truncate( 1m0s) = 12:15:00
t.Truncate(10m0s) = 12:10:00

func (Time) UTC 

func (t Time) UTC() Time

UTC returns t with the location set to UTC.

func (Time) Unix 

func (t Time) Unix() int64

Unix returns t as a Unix time, the number of seconds elapsed since January 1, 1970 UTC. The result does not depend on the location associated with t. Unix-like operating systems often record time as a 32-bit count of seconds, but since the method here returns a 64-bit value it is valid for billions of years into the past or future.

Example 
package main

import (
	"fmt"
	"time"
)

func main() {
	// 1 billion seconds of Unix, three ways.
	fmt.Println(time.Unix(1e9, 0).UTC())     // 1e9 seconds
	fmt.Println(time.Unix(0, 1e18).UTC())    // 1e18 nanoseconds
	fmt.Println(time.Unix(2e9, -1e18).UTC()) // 2e9 seconds - 1e18 nanoseconds

	t := time.Date(2001, time.September, 9, 1, 46, 40, 0, time.UTC)
	fmt.Println(t.Unix())     // seconds since 1970
	fmt.Println(t.UnixNano()) // nanoseconds since 1970

}

Output:

2001-09-09 01:46:40 +0000 UTC
2001-09-09 01:46:40 +0000 UTC
2001-09-09 01:46:40 +0000 UTC
1000000000
1000000000000000000

func (Time) UnixMicro added in go1.17 

func (t Time) UnixMicro() int64

UnixMicro returns t as a Unix time, the number of microseconds elapsed since January 1, 1970 UTC. The result is undefined if the Unix time in microseconds cannot be represented by an int64 (a date before year -290307 or after year 294246). The result does not depend on the location associated with t.

func (Time) UnixMilli added in go1.17 

func (t Time) UnixMilli() int64

UnixMilli returns t as a Unix time, the number of milliseconds elapsed since January 1, 1970 UTC. The result is undefined if the Unix time in milliseconds cannot be represented by an int64 (a date more than 292 million years before or after 1970). The result does not depend on the location associated with t.

func (Time) UnixNano 

func (t Time) UnixNano() int64

UnixNano returns t as a Unix time, the number of nanoseconds elapsed since January 1, 1970 UTC. The result is undefined if the Unix time in nanoseconds cannot be represented by an int64 (a date before the year 1678 or after 2262). Note that this means the result of calling UnixNano on the zero Time is undefined. The result does not depend on the location associated with t.

func (*Time) UnmarshalBinary added in go1.2 

func (t *Time) UnmarshalBinary(data []byte) error

UnmarshalBinary implements the encoding.BinaryUnmarshaler interface.

func (*Time) UnmarshalJSON 

func (t *Time) UnmarshalJSON(data []byte) error

UnmarshalJSON implements the [json.Unmarshaler] interface. The time must be a quoted string in the RFC 3339 format.

func (*Time) UnmarshalText added in go1.2 

func (t *Time) UnmarshalText(data []byte) error

UnmarshalText implements the encoding.TextUnmarshaler interface. The time must be in the RFC 3339 format.

func (Time) Weekday 

func (t Time) Weekday() Weekday

Weekday returns the day of the week specified by t.

func (Time) Year 

func (t Time) Year() int

Year returns the year in which t occurs.

func (Time) YearDay added in go1.1 

func (t Time) YearDay() int

YearDay returns the day of the year specified by t, in the range [1,365] for non-leap years, and [1,366] in leap years.

func (Time) Zone 

func (t Time) Zone() (name string, offset int)

Zone computes the time zone in effect at time t, returning the abbreviated name of the zone (such as "CET") and its offset in seconds east of UTC.

func (Time) ZoneBounds added in go1.19 

func (t Time) ZoneBounds() (start, end Time)

ZoneBounds returns the bounds of the time zone in effect at time t. The zone begins at start and the next zone begins at end. If the zone begins at the beginning of time, start will be returned as a zero Time. If the zone goes on forever, end will be returned as a zero Time. The Location of the returned times will be the same as t.

type Timer 

type Timer struct {
	C <-chan Time
	// contains filtered or unexported fields
}

The Timer type represents a single event. When the Timer expires, the current time will be sent on C, unless the Timer was created by AfterFunc. A Timer must be created with NewTimer or AfterFunc.

func AfterFunc 

func AfterFunc(d Duration, f func()) *Timer

AfterFunc waits for the duration to elapse and then calls f in its own goroutine. It returns a Timer that can be used to cancel the call using its Stop method. The returned Timer's C field is not used and will be nil.

func NewTimer 

func NewTimer(d Duration) *Timer

NewTimer creates a new Timer that will send the current time on its channel after at least duration d.

Before Go 1.23, the garbage collector did not recover timers that had not yet expired or been stopped, so code often immediately deferred t.Stop after calling NewTimer, to make the timer recoverable when it was no longer needed. As of Go 1.23, the garbage collector can recover unreferenced timers, even if they haven't expired or been stopped. The Stop method is no longer necessary to help the garbage collector. (Code may of course still want to call Stop to stop the timer for other reasons.)

Before Go 1.23, the channel associated with a Timer was asynchronous (buffered, capacity 1), which meant that stale time values could be received even after Timer.Stop or Timer.Reset returned. As of Go 1.23, the channel is synchronous (unbuffered, capacity 0), eliminating the possibility of those stale values.

The GODEBUG setting asynctimerchan=1 restores both pre-Go 1.23 behaviors: when set, unexpired timers won't be garbage collected, and channels will have buffered capacity. This setting may be removed in Go 1.27 or later.

func (*Timer) Reset added in go1.1 

func (t *Timer) Reset(d Duration) bool

Reset changes the timer to expire after duration d. It returns true if the timer had been active, false if the timer had expired or been stopped.

For a func-based timer created with AfterFunc(d, f), Reset either reschedules when f will run, in which case Reset returns true, or schedules f to run again, in which case it returns false. When Reset returns false, Reset neither waits for the prior f to complete before returning nor does it guarantee that the subsequent goroutine running f does not run concurrently with the prior one. If the caller needs to know whether the prior execution of f is completed, it must coordinate with f explicitly.

For a chan-based timer created with NewTimer, as of Go 1.23, any receive from t.C after Reset has returned is guaranteed not to receive a time value corresponding to the previous timer settings; if the program has not received from t.C already and the timer is running, Reset is guaranteed to return true. Before Go 1.23, the only safe way to use Reset was to [Stop] and explicitly drain the timer first. See the NewTimer documentation for more details.

func (*Timer) Stop 

func (t *Timer) Stop() bool

Stop prevents the Timer from firing. It returns true if the call stops the timer, false if the timer has already expired or been stopped.

For a func-based timer created with AfterFunc(d, f), if t.Stop returns false, then the timer has already expired and the function f has been started in its own goroutine; Stop does not wait for f to complete before returning. If the caller needs to know whether f is completed, it must coordinate with f explicitly.

For a chan-based timer created with NewTimer(d), as of Go 1.23, any receive from t.C after Stop has returned is guaranteed to block rather than receive a stale time value from before the Stop; if the program has not received from t.C already and the timer is running, Stop is guaranteed to return true. Before Go 1.23, the only safe way to use Stop was insert an extra <-t.C if Stop returned false to drain a potential stale value. See the NewTimer documentation for more details.

type Weekday 

type Weekday int

A Weekday specifies a day of the week (Sunday = 0, ...). 

const (
	Sunday Weekday = iota
	Monday
	Tuesday
	Wednesday
	Thursday
	Friday
	Saturday
)

func (Weekday) String 

func (d Weekday) String() string

String returns the English name of the day ("Sunday", "Monday", ...).

Source Files

View all Source files

Directories

Path Synopsis
Package tzdata provides an embedded copy of the timezone database.
 Package tzdata provides an embedded copy of the timezone database.

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