PHP: Manual: mktime

Description

int mktime (int hour, int minute, int second, int month, int day, int year [, int is_dst])

Warning: Note the strange order of arguments, which differs from the order of arguments in a regular UNIX mktime() call and which does not lend itself well to leaving out parameters from right to left (see below). It is a common error to mix these values up in a script.

Returns the Unix timestamp corresponding to the arguments given. This timestamp is a long integer containing the number of seconds between the Unix Epoch (January 1 1970) and the time specified.

Arguments may be left out in order from right to left; any arguments thus omitted will be set to the current value according to the local date and time.

Is_dst can be set to 1 if the time is during daylight savings time, 0 if it is not, or -1 (the default) if it is unknown whether the time is within daylight savings time or not.

Note: Is_dst was added in 3.0.10.

Mktime() is useful for doing date arithmetic and validation, as it will automatically calculate the correct value for out-of-range input. For example, each of the following lines produces the string "Jan-01-1998".
Example 1. Mktime() example
echo date ("M-d-Y", mktime (0,0,0,12,32,1997)); echo date ("M-d-Y", mktime (0,0,0,13,1,1997)); echo date ("M-d-Y", mktime (0,0,0,1,1,1998)); echo date ("M-d-Y", mktime (0,0,0,1,1,98));
Year may be a two or four digit value, with values between 0-69 mapping to 2000-2069 and 70-99 to 1970-1999 (on systems where time_t is a 32bit signed integer, as most common today, the valid range for year is somewhere between 1902 and 2037).

The last day of any given month can be expressed as the "0" day of the next month, not the -1 day. Both of the following examples will produce the string "The last day in Feb 2000 is: 29".
Example 2. Last day of next month
$lastday = mktime (0,0,0,3,0,2000); echo strftime ("Last day in Feb 2000 is: %d", $lastday); $lastday = mktime (0,0,0,4,-31,2000); echo strftime ("Last day in Feb 2000 is: %d", $lastday);

Date with year, month and day equal to zero is considered illegal (otherwise it what be regarded as 30.11.1999, which would be strange behaviour).