Calendar reform
Calendar reform, properly calendrical reform, is any significant revision of a calendar system. The term sometimes is used instead for a proposal to switch to a different calendar.
Most calendars have several rules which could be altered by reform:
Whether and how days are grouped into subdivisions such as months and weeks, and days outside those subdivisions, if any.
Which years are leap years and common years and how they differ.
Numbering of years, selection of the epoch, and the issue of year zero.
Start of the year (such as southern solstice, January 1, March 1, northward equinox, Easter).
If a week is retained, the start, length, and names of its days.
Start of the day (midnight, sunrise, noon, or sunset).
If months are retained, number, lengths, and names of months,
Special days and periods (such as leap day or intercalary day).
Alignment with social cycles.
Alignment with astronomical cycles.
Alignment with biological cycles.
Literal notation of dates.
Historical reforms
