Thanks, Chad - here's what I ended up doing...
I set my start and stop time QuestionOptionValues to be in the 24-hour format HH:MM, then just converted them to the datetime format and updated:
update Recruitment_Input_Meetings set MeetingDateStart = cast(TimeStart as datetime) from [dbo].[Recruitment_Input_Meetings];
update Recruitment_Input_Meetings set MeetingDateStop = cast(TimeStop as datetime) from [dbo].[Recruitment_Input_Meetings]
Thanks for the pointers!
~Patrick