It can be hard sometimes,but here is an explanation of telling the difference:

This is good info for "yearlings"......but I know for my circumstances....a "fawn" out of spots is this year's dear. Once they lose their spots, here.....I'm considering them fair game ....as long as they are does.

I'll take all the help I can get in determining how to distinguish this year's deer. I have no problems with yearlings. My field glasses were purchased, mainly, for this reason.