DATE returns the number of days since the 1st of january of 1900(the date serial number) for the given year, month and day.
The @day might be negative (to count backwards) and it is relative to the previous @month. The @years should be at least 1900. If @years <= 30, it is assumed to be 2000 + @years. If 30 < @years < 100, it is assumed to be 1900 + @years.
If the given date is not valid, DATE returns #VALUE! error.
This function is Excel compatible.