I don't find time outs work at that age. I do what I call a "time away"....the child is removed from the others (just to a different area in the playroom) and given a toy or book to read. I tell them in simple words why they are separated "No pinching. Not nice. You play here for a bit". Than after a minute or two I encourage them to come back and "Play nice. No pinching". I will keep doing this over and over. They are still young and we have to teach them what is acceptable play and what isn't.
I find once they get closer to two than timeouts start to work. Some kids can understand time outs around 20 or so months though depending on their mental age.