Makes sense. For the most part, many of the characters are around the same age as their actors.Okay so there's no indication when that flashback (in the most recent Legends episode) Nate has to his college years takes place. Because I have no idea what his age is other than he grew up in the 80s. I could maybe base it off of the actual age of Nick Zano (Nate's actor) but I'm not sure about that. He looks really good for someone who was born in 1978.
EDIT: So Nate went to college at age 16, and you would need 9 years to get a PhD in History, he'd be around 25 when he graduated. He does not look to be freshly out of college by the time he first appears in the Arrowverse (Legends s2 premiere) so I'd have to say he'd be at least 10 years older, closer to age 38 when the actor filmed Legends' second season.
I don't want to get too complicated, so I'll assume he's 40; closer to the actor's current age. In his college years flashback I'll also assume this was when was just starting out.
I'll go with a "????" in the mid 90s.