These functions allow you to get the date and time from the server
where your PHP scripts are running. You can use these functions to format the
date and time in many different ways.
Note:
Please keep in mind that these functions are dependent on
the locale settings of your server. Make sure to take
daylight saving time (use e.g.
$date = strtotime('+7 days', $date) and not
$date += 7*24*60*60)
and leap years into consideration when working
with these functions.
The default timezone used by all date/time functions if the
TZ environment variable isn't set. The precedence
order is described in the date_default_timezone_get()
page.
The following constants are defined since PHP 5.1.0 and they offer standard
date representations, which can be used along with the date format functions
(like date()).