int GetDay() const;
Returns the day of the month, based on local time, in the range 1 through 31.
CTime t( 1999, 3, 19, 22, 15, 0 ); // 10:15PM March 19, 1999
ASSERT( t.GetDay() == 19 );
ASSERT( t.GetMonth() == 3 );
ASSERT( t.GetYear() == 1999 );