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SET DATEFIRST (Transact-SQL)
Sets the first day of the week to a number from 1 through 7.
The following example displays the day of the week for a date value and shows the effects of changing the
-- SET DATEFIRST to U.S. English default value of 7. SET DATEFIRST 7; SELECT CAST('1/1/1999' AS DATETIME) AS SelectDate, DATEPART(dw, '1/1/1999') AS DayOfWeek; -- January 1, 1999 is a Friday. Because the U.S. English default -- specifies Sunday as the first day of the week, DATEPART of 1/1/1999 -- (Friday) yields a value of 6, because Friday is the sixth day of the -- week when starting with Sunday as day 1. SET DATEFIRST 3; -- Because Wednesday is now considered the first day of the week, -- DATEPART should now show that 1/1/1999 (a Friday) is the third day of the -- week. The following DATEPART function should return a value of 3. SELECT CAST('1/1/1999' AS DATETIME) AS SelectDate, DATEPART(dw, '1/1/1999') AS DayOfWeek; GO