DECLARE @ClarionDate INT = 47563 DECLARE @SqlDateTime DATETIME -- Convert the clarion DATE into and SQL DateTime SET @SqlDateTime = DateAdd(day, @ClarionDate - 4, '1801-01-01') SELECT @SqlDateTime AS 'SQL Date Time' -- Now convert it back from and SQL DateTime to a Clarion Date SET @ClarionDate = DateDiff(day, DateAdd(day, -4, '1801-01-01'), @SqlDateTime) SELECT @ClarionDate AS 'Clarion Date'