According to a couple big game biologists here in ND, a fawn is a fawn until the following spring when it turns one year old, then it is termed a yearling and remains so until it's second birthday, if it gets one. So here in ND, it is a yearling about the first of June because most fawns are born the first two weeks of June.

I asked about spots and weening and they responded that neither has anything to do with terming a deer as a fawn or yearling, it is strictly age.