Is My_Billing_Date of data type Date or is it of type String?
You can avoid the ambiguities encountered with date formats by creating a new date object instead of using a string. To create a date object, use: New Date(yr, mo, da) Where yr is the 4 digit year, mo is the month (zero based, so January is 0), and da is the day of the month.
For your computed column, you could say:
MonthsBetween (YTD_Billing_Date, new Date(2002, 6, 1));
This formula would calcuate the number of months between YTD_Billing_Date and July 1, 2002.
