If the current date is October 18, 2010, which is a Monday, the following queries return the value 2 as the result since Monday is the 2nd day of the week.
SELECT td_day_of_week(CURRENT_DATE); SELECT td_day_of_week(DATE '2010-10-18');
SELECT DAYOFWEEK(CURRENT_DATE); SELECT DAYOFWEEK(DATE '2010-10-18');