How to tell a bettas age

[Goldmoon]

Hello everyone! I was just wondering if there are any ways to tell how old a betta is. PetSmart employees don’t know how old the fish are when they get them in and I have quite a few males from there I’d like to know the age of. I’ve googled how to tell/estimate age multiple times but don’t ever really get a clear/straightforward answer. Any and all help/advice will be greatly appreciated! Thanks in advance!

[SaraB]

The ones in the store are usually a few months old. That's what I was told anyways. Other than that I don't really think there's an exact way to tell.