Time - Morning/Afternoon/Evening --- Thanks!!!
The clarification is needed because a date/time field can't have 24:00
Try this:-
IIf(IsNull([Time]),Null, IIf(Format([Time],"hh:nn:ss")<="12:00:00","Morning", IIf(Format([Time],"hh:nn:ss")<="18:00:00","Afternoon","Evening")))...