@DATE — Converts the specified date into an MS-DOS day number, with 0 being January 1, 1980. The date argument may be in any input date format supported by this plugin, and must be a valid date within the supported range. If the date is before 1980, the value returned will be negative.

Syntax:
%@DATE[date,infmt]

datethe date to convert; if omitted, uses today’s date
infmtthe input date format, used to interpret ambiguous dates

See also: @MAKEDATE, which performs the reverse function.