[date/time] Return a bool from SetDate/Time to indicate a successful, valid, date
[date/time] validate SetFromDBDate() a little better
[date/time] have SetFromDateString() first attempt SetFromDBDate() before attempting to parse for a 'Sunday, April 15 2006' style date
Merge pull request #3953 from jmarshallnz/date_time_validation

Date time validation