Since my date is well formatted now all there is left for me to do is to print milliseconds too.
I already tried setDateFormat yyyy/mm/dd hh:mm:ss:ms
That didn't work. Any advice?
Try to use 'SS' specifier (with number of S's equal to number of digits you want to get - 3 in your case), e.g.
[formatter setDateFormat:@"yyyy/MM/dd hh:mm:ss:SSS"];