This duration is usually 1 hour, but it can be 30 or 45 minutes, depending on time zone. When the clock's set ahead, there's a gap in local time equal to the duration of the clock adjustment. RemarksĪT TIME ZONE applies specific rules for converting input values in smalldatetime, datetime, and datetime2 data types that fall into an interval affected by a DST change: The datetimeoffset value in the target time zone.
A list of installed time zones is also exposed through the sys.time_zone_info (Transact-SQL) view. Time zones installed on the computer are stored in the following registry hive: KEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Time Zones. SQL Server relies on time zones that are stored in the Windows Registry. Is an expression that can be resolved to a smalldatetime, datetime, datetime2, or datetimeoffset value. Transact-SQL Syntax Conventions Syntax inputdate AT TIME ZONE timezone
If inputdate is provided as a datetimeoffset value, then AT TIME ZONE clause converts it into the target time zone using the time zone conversion rules.ĪT TIME ZONE implementation relies on a Windows mechanism to convert datetime values across time zones. When inputdate is provided without offset information, the function applies the offset of the time zone assuming that inputdate is in the target time zone. This will affect subsequent operations and conversions from TIMESTAMP to TIMESTAMPTZ - just make sure to get it right.Īfter you have converted all timestamps to TIMESTAMPTZ, server or client timezone setting (which defaults to current operating system timezone setting) is only useful for display purposes, as data manipulation will be always correct.Applies to: SQL Server 2016 (13.x) and later Azure SQL Database Azure SQL Managed Instance Azure Synapse AnalyticsĬonverts an inputdate to the corresponding datetimeoffset value in the target time zone. If conversion does not work correctly, you can temporarily set timezone for current session (you need it only for conversion purposes) using statement like (use it before ALTER TABLE. You should be able to convert your existing TIMESTAMP columns into TIMESTAMPTZ using something like: ALTER TABLE mytable ALTER COLUMN old_tstamp TYPE TIMESTAMPTZīefore doing this, you should experiment on small dataset or maybe small test table on how conversion from TIMESTAMP to TIMESTAMPTZ is really working for you such that time zone information is preserved on your data. This allows you to always manipulate and display these columns correctly, no matter what current server or client timezone setting is.
TIMESTAMPTZ stores both timestamp in UTC and timezone in which timestamp was originally written to (like CST, PST or GMT+6).
Well, best practice is to avoid using TIMESTAMP type which does not know anything about timezones and to always use TIMESTAMPTZ (short for TIMESTAMP WITH TIME ZONE) type to store your timestamps.
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