interp1 will work...
dt=datetime(2020,11,18,00,1+[0:30].',0);
dt20=datetime(2020,11,17,0,[20:30:2400].',0);
>> interp1(dt20,dt20,dt,'nearest')
ans =
31×1 datetime array
17-Nov-2020 23:50:00
17-Nov-2020 23:50:00
17-Nov-2020 23:50:00
17-Nov-2020 23:50:00
18-Nov-2020 00:20:00
18-Nov-2020 00:20:00
18-Nov-2020 00:20:00
18-Nov-2020 00:20:00
18-Nov-2020 00:20:00
18-Nov-2020 00:20:00
18-Nov-2020 00:20:00
18-Nov-2020 00:20:00
18-Nov-2020 00:20:00
18-Nov-2020 00:20:00
18-Nov-2020 00:20:00
18-Nov-2020 00:20:00
18-Nov-2020 00:20:00
18-Nov-2020 00:20:00
18-Nov-2020 00:20:00
18-Nov-2020 00:20:00
18-Nov-2020 00:20:00
18-Nov-2020 00:20:00
18-Nov-2020 00:20:00
18-Nov-2020 00:20:00
18-Nov-2020 00:20:00
18-Nov-2020 00:20:00
18-Nov-2020 00:20:00
18-Nov-2020 00:20:00
18-Nov-2020 00:20:00
18-Nov-2020 00:20:00
18-Nov-2020 00:20:00
>>
There's probably more clever ways...
Best Answer