I think most guys err on the conservative side when it comes to aging deer from looking at pictures...not that it's a bad thing.
This buck looks pretty filled out in the neck and body and has good tine length so I'd say he's a 3.5 year old.
Edit: I didn't see the daylight photo first time, but seeing now that the main beams aren't that long I'm gonna have to lean toward a 2.5 year old with pretty good genetics and eatin well. Almost looks like he has two main beams on his left side. Nice buck.