sql server 2008 – SQL: Using DATEADD with bigints

August 19, 2024admin

I had the same problem and I wanted to be meet the datetime range of mssql

Minimun datetime: 1753-01-01 00:00:00.000 (-6847804800)
Maximum datetime: 9999-12-31 23:59:59.997 (253402300799)

To achieve this the only solution I found was to loop to use DATEADD with int range values.

So based on this answer: stackoverflow.com/a/2904294/687490

CREATE FUNCTION dbo.fn_ConvertToBigDateTime (@Datetime BIGINT)
RETURNS DATETIME
AS
BEGIN
    DECLARE @result datetime = Convert(datetime, '01/01/1970');

    DECLARE @LocalTimeOffset BIGINT
           ,@AdjustedLocalDatetime BIGINT
           ,@MinIntValue INT
           ,@MaxIntValue INT
           ,@RemainingSeconds BIGINT;

    -- define int limit
    SET @MinIntValue = -2147483648;
    SET @MaxIntValue = 2147483647;

    -- compute the datetime with the offset
    SET @LocalTimeOffset = DATEDIFF(second,GETDATE(),GETUTCDATE())
    SET @AdjustedLocalDatetime = @Datetime - @LocalTimeOffset

    -- going to the future
    WHILE(@AdjustedLocalDatetime>@MaxIntValue)
    BEGIN
        SET @AdjustedLocalDatetime = @AdjustedLocalDatetime - @MaxIntValue;
        SELECT @result = Convert(datetime, dateadd(ss, @MaxIntValue,@result));
    END

    -- going back in the past
    WHILE(@AdjustedLocalDatetime<@MinIntValue)
    BEGIN
        SET @AdjustedLocalDatetime = @AdjustedLocalDatetime - @MinIntValue;
        SELECT @result = Convert(datetime, dateadd(ss, @MinIntValue,@result));
    END

    RETURN (SELECT DATEADD(second,@AdjustedLocalDatetime, @result))
END;

You can then test the function with :

select dbo.fn_ConvertToBigDateTime(-6847804800) as 'min datetime', 
dbo.fn_ConvertToBigDateTime(253402300799) as 'max datetime'

Hope it will help.