timetable1 is not a timetable, and probably not even legal MATLAB code. I'm going to assume you mean that you have an actual timetable with datetime row times and one numeric variable. And a list of datetimes at which you want to select rows of your timetable.
Just subscript the timetable with the datetimes. That's it.
>> tt = timetable([1;2;3;4;5],'RowTimes',datetime(2020,11,18:22))
tt =
5×1 timetable
Time Var1
___________ ____
18-Nov-2020 1
19-Nov-2020 2
20-Nov-2020 3
21-Nov-2020 4
22-Nov-2020 5
>> tt(datetime(2020,11,[18 20 22]),:)
ans =
3×1 timetable
Time Var1
___________ ____
18-Nov-2020 1
20-Nov-2020 3
22-Nov-2020 5
You should also take a look at timerange, which is a way to create a subscript that will select rows in a range rather tha exact matches.