The range of date time value that we can pass as an argument to MySQL UNIX_TIMESTAMP function is the same as the range of TIMESTAMP data type i.e. between ‘1970-01-01 00:00:01’ to ‘2038-01-19 08:44:07’. If we give the date time values in UNIX_TIMESTAMP function beyond or below TIMESTAMP range, MySQL will return 0 as output. It can be understood with the help of the following example −
mysql> select UNIX_TIMESTAMP('2038-01-19 08:44:07');
+---------------------------------------+
| UNIX_TIMESTAMP('2038-01-19 08:44:07') |
+---------------------------------------+
| 2147483647 |
+---------------------------------------+
1 row in set (0.00 sec)
mysql> select UNIX_TIMESTAMP('2038-01-19 08:44:08');
+---------------------------------------+
| UNIX_TIMESTAMP('2038-01-19 08:44:08') |
+---------------------------------------+
| 0 |
+---------------------------------------+
1 row in set (0.00 sec)
mysql> select UNIX_TIMESTAMP('1969-01-01 05:10:00');
+---------------------------------------+
| UNIX_TIMESTAMP('1969-01-01 05:10:00') |
+---------------------------------------+
| 0 |
+---------------------------------------+
1 row in set (0.00 sec)