rem: DateTime& operator=(const QDate& d) { mDateTime.setDate(d);  mDateOnly = true;  return *this; }
add: DateTime::operator = (const DateTime & t) { if (this == &t) return *this; qdate_  = t.qdate_; zone_   = t.zone_.copy();  HeaderBody::operator = (t); return *this; }
context: 		DateTime& operator=(const QDate& d)		                               { mDateTime.setDate(d);  mDateOnly = true;  return *this; }