Board Thread:General Discussion/@comment-27324545-20160105135410

Assuming that Papyrus and Undyne's birth year is what is shown at the end of their Undernet usernames (Napstablook too, maybe), we kinda have an idea of their age range. Everybody else is who knows how old (Toriel and Asgore must be pretty up there since they don't age anymore).

I'm just curious about what you guys think the monsters ages are. Mains, NPC's, vendors, anyone is fair game. Just keep in mind that this is an opinionated post, so unless Toby Fox himself confirms anything, none is fact. Enjoy! 