const CTime& operator +=( CTimeSpan timeSpan );
const CTime& operator –=( CTimeSpan timeSpan );
These operators allow you to add and subtract a CTimeSpan object to and from this CTime object.
CTime t( 1999, 3, 19, 22, 15, 0 ); // 10:15PM March 19, 1999
t += CTimeSpan( 0, 1, 0, 0 ); // one hour exactly
ASSERT( t.GetHour() == 23 );