Absolute time in seconds since January 1, 1900:

Convert from a date object to an absolute time:

Convert a date list or elided date list:

Convert from a date string to absolute time:

Specify date elements for interpreting a string:

Strings are automatically interpreted when possible:

Separators are assumed if not specified:

Give explicit separators:

Date lists are converted to standard normalized form:

Day, hour, minute, and second values in input date lists can be noninteger:

The current year is used if not specified in a string:

Give explicit date elements to interpret ambiguous strings:

Use DateListPlot to plot data with absolute time coordinates on a time scale:

Compute the number of seconds between January 1, 1900, and January 1, 2000:

AbsoluteTime represents dates as seconds since the beginning of 1900:

DateObject represents a given date:

DateList represents dates as lists of date elements:

DateString represents dates as strings:

The number of seconds returned by AbsoluteTime corresponds to the "AbsoluteTime" calendar:

UnixTime returns the number of seconds since the beginning of 1970, in the GMT time zone:

Therefore this difference is constant:

It is the number of seconds since January 1, 1900, to January 1, 1970:

JulianDate returns the number of days since noon on November 24, 4714 BCE in the GMT time zone:

Therefore this difference is constant:

It is the number of seconds since noon on November 24, 4714 BCE, to the beginning of January 1, 1900:

That proleptic Gregorian date is noon on January 1, 4713 BCE in the Julian calendar: