Date[ ] gives the current local date and time in the form year, month, day, hour, minute, second.
Date[ ] uses whatever date and time have been set on your computer system. It performs no corrections for time zones, daylight saving time, etc.
Date[z] gives the date in time zone z. This is inferred by knowing your local date and time, and local time zone. The time zone is given as the number of hours to be added to Greenwich mean time to obtain local time.
All values returned by Date[ ] are integers, except the number of seconds. The number of seconds is never more accurate than $TimeUnit.
You can compare two lists returned by Date using Order.
See The Mathematica Book: Section 2.13.3.
See also: AbsoluteTime, TimeZone, SessionTime, TimeUsed, ToDate, FromDate, FileDate, $CreationDate.
Related package: Miscellaneous`Calendar`.