DAY (date) — yields the number of the weekday on which the specified date falls (where Sun=1, Mon=2, etc.).
SELECT DAY(03/22/06) FROM DUMMY FORMAT; /* 4 */
Note: This number can then be translated into the name of the weekday by means of the DAYS table (for the application's base language of English) and the LANGDAYS table (for any additional languages). These tables store the names of all days in the week in what ever language you are using.