DateTimeminusDays

DateTimeminusDays is a date-time manipulation operation that returns a new DateTime value by subtracting a specified number of days from a given DateTime input. It is common in programming languages, data-processing tools, and database libraries, though the exact syntax and naming vary.

Parameters and return: The function typically accepts two operands: baseDateTime (the starting DateTime) and daysToSubtract (an integer). The return is a DateTime representing baseDateTime minus daysToSubtract days. When daysToSubtract is negative, the effect is to add days.

Implementation notes: Across languages, similar behavior is achieved by using a duration subtraction or by calling a function AddDays(-n). Timezone handling depends on the library: some preserve the same timezone, others operate in UTC or local time. Subtracting days generally preserves the time-of-day component unless the library normalizes.

Edge cases: Crossing month or year boundaries, and leap days (February 29) are handled according to the calendar. In some time zones, daylight saving time transitions can affect the wall clock time when moving across days, depending on how the library represents and normalizes times.

Examples: DateTimeminusDays("2024-03-01T12:00:00", 5) yields "2024-02-25T12:00:00" in systems that preserve the time-of-day. Subtracting 0 returns the input. If daysToSubtract is negative, the operation effectively adds days.

See also: DateTime_AddDays, DateAdd, TimeSpan, duration-based date arithmetic.