מה-SDK:
Special Date Columns
As mentioned earlier, dates are stored in Priority as integers, which correspond to the number of minutes elapsed since Jan. 1, 1988 (for example, Dec. 31, 1987 = -1440). Hence, the date 01/01/1988 is stored as "0". Since Priority forms do not generally display zero values, this date is not displayed in form columns. If you want the value 01/01/1988 to be displayed in a particular column, the form column name must contain the string BIRTHDATE (e.g., the BIRTHDATE10 column in the USERSB_ONE form).