SWITCHOFFSET

SWITCHOFFSET is a Transact-SQL function in Microsoft SQL Server that changes the time zone offset of a datetimeoffset value while preserving the same absolute (UTC) moment in time. It returns a datetimeoffset value whose local time is adjusted so that the underlying UTC instant remains unchanged.

Syntax and usage typically appear as:

SWITCHOFFSET(datetimeoffset_value, target_offset)

where target_offset is a string in the form '+HH:MM' or '-HH:MM'. For example, SWITCHOFFSET('2021-03-15 10:00:00 -05:00', '+00:00') yields '2021-03-15 15:00:00 +00:00'.

Key characteristics:

- The function shifts the local datetime by the difference between the original offset and the target offset, keeping the UTC point constant.

- It accepts datetimeoffset inputs and produces datetimeoffset outputs.

- It does not perform time zone name-based conversions or apply daylight saving time rules; it operates solely on numeric offsets.

- For conversions that require time zone rules or DST awareness, the AT TIME ZONE construct (introduced in SQL Server 2016) is more appropriate.

- SWITCHOFFSET differs from TODATETIMEOFFSET: TODATETIMEOFFSET attaches a specified offset to a datetime value without preserving the original UTC instant, while SWITCHOFFSET preserves the instant and alters the local time.

Common uses include normalizing stored datetimeoffset values to a standard offset (such as UTC) or displaying a stored UTC instant in a specified offset for presentation.