"I would like to extract the data by months (for example all January months along 2010 and 2019)."
To do what?
If you want to calculate some monthly statistics, this can be done in just one line of code (for all the months at once).
timerange is not suitable for non-contiguous range. But it's easy enough to discretise a datetime vector by month if that's what you really need.
But again, what are you trying to do?
edit: Oh and please don't post screenshots of code. Paste the code so that we can in turn paste it into matlab.
Also, datetime arrays are very easy to work with. You should never have a need to use the outdated datestr and datenum. Your whole |timerange construction is way too complicated:
start = datetime(year1, month1, day1);
final = datetime(yeat2, month2, day2);
Sa = timerange(start, final);
