Class date is designed for working with dates. Possible variants of using it include: calendars, various checks based on dates, etc.
Values may range from 01/01/1970 to 01/01/2038.
Do not forget that we have different gaps and overlaps: many countries have so-called Daylight Saving Time, when clock is set ahead (in spring) or back (in autumn) one hour.
For example, in Moscow, there cannot be "02:00, 31 March 2002," while "02:00, 27 October 2002" can be twice.
Numeric value of object of class date equals to the number of days from EPOCH (00:00:00, 1 January 1970, UTC) to the date specified in the object. This feature is useful when you want to get a relative date, e.g.:
# checking if the file was updated more than a week ago
^if($last_update > $now-7){
new
}{
old
}
The number of days can be fractional, e.g. a day and half is equal to 1.5.
The class usually operates local date and time. Still, you can get date and time in arbitrary time zone (see ^date.roll[TZ;…].
To communicate between computers that are in different time zones it is convinient to exchange values of date/time which do not depend on timezone-UNIX format, which is number of seconds passed since EPOCH, is very convinient here.
Unix format can be used in JavaScript and several other scripting languages that work in browser.