Please try this
DECLARE @Datetime BIGINT, @Result datetime, @LocalDatetime BIGINT;
SET @Datetime = 1395774998
SET @LocalDatetime = @Datetime - DATEDIFF(second,GETDATE(),GETUTCDATE())
SET @Result = (SELECT DATEADD(second,@LocalDatetime , CAST('1970-01-01 00:00:00' AS datetime)))
select @Result
OR function
CREATE FUNCTION dbo.ufn_ConvertUnixTimestampToDateTime (@Datetime BIGINT)
RETURNS DATETIME
AS
BEGIN
DECLARE @LocalDatetime BIGINT
SET @LocalDatetime = @Datetime - DATEDIFF(second,GETDATE(),GETUTCDATE())
RETURN (SELECT DATEADD(second,@LocalDatetime, CAST('1970-01-01 00:00:00' AS datetime)))
END;