Date values and time values have an associated origin or epoch, which is a moment in time from which time begins. Any date value and any time value prior to its epoch is invalid.The unit of value for all date functions is the number of days since the epoch. The unit of value for all time functions is the number of milliseconds since the epoch.LiveCycle Designer ES defines day one for the epoch for all date functions as Jan 1, 1900, and millisecond one for the epoch for all time functions is midnight, 00:00:00, Greenwich Mean Time (GMT). This definition means that negative time values can be returned to users in time zones east of GMT.