A date is an ambiguous interval in time, which usually refers to a day, month, and year in a particular calendar system.
A date by itself (such as
Jan 1 2014) does not refer to a specific moment in time.
- It does not have a time of day, so it refers to a whole calendar date.
- It does not specify a time zone, so it could be interpreted differently by each viewer.
Related concepts such as "today", "yesterday", and "tomorrow", or any individual day of the week such as "Monday" or "Tuesday", also have the same qualities. They are loose terms that require a time zone in order to lock in to a specific range of time.
Date type actually represents a date and time of day and is therefore misnamed.
The most recognized calendar is the Gregorian calendar, but there are other known calendars such as the Hebrew or the Hijri (Muslim) calendar. Since both start at a different date from the Gregorian calendar's date, the dates in these calendars are different. When one intends to implement an international application or website, the different calendars might be good to be taken into account.
See also: datetime, time, timezone and dst