ORIGINAL: rybohunter
I do believe they are telling you that they're that accurate, but there's absolutely no way they can tell that close. There's no guarantee that they are within a year, let alone a month. It's simply an educated guess.
If they grind them down and do a ring count, I believe that is as accurate as it gets and is pretty much exact.
Actually, it's stillnot 100% accurate, but closer. The rings don't indicate one year like we think with trees. Each ring indicates a period of stress for the deer, usually assumed to be winter. If winter was the only period of stress for a deerduiring its life, those rings would be accurate. However, a period of stress could also be an injury, or drought,or change in environment. The rings will tell the maximum age a deer can be, but they can't guarantee the deers age.
Nothing short of an ear tag can give an exact age.