mktime
mktime -- 지정된 날짜를 date()함수 등이 사용하는 timestamp로 만든다.

Description
int mktime (int hour, int minute, int second, int month, int day, int year [, int is_dst])
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
date ("M-d-Y", mktime (0,0,0,12,32,1997));
date ("M-d-Y", mktime (0,0,0,13,1,1997));
date ("M-d-Y", mktime (0,0,0,1,1,1998));
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);
strftime ("Last day in Feb 2000 is: %d", $lastday);
$lastday = mktime (0,0,0,4,-31,2000);
strftime ("Last day in Feb 2000 is: %d", $lastday);
( 역자주 : 다음과 같이 date() 함수를 같이 사용하면 과거나 미래의 특정일을 알 수 있다.

$tomorrow = mktime(0,0,0,date("d")+1,date("m"), date("Y"));
$lastmonth = mktime(0,0,0,date("d"),date("m")-1,date("Y"));
$nextyear = mktime(0,0,0,date("d"),date("m"),date("Y")+1); )