Being the massive Friends fan that I am, I'll try to piece together the information and come up with an answer.
We first have to look at the Thanksgiving episode The One with all the Thanksgivings. Ross introduces Chandler as his roommate and band member.
Ross: (entering) Hey!
Mr. Geller: Oh my!
Ross: Uh, everyone, this is Chandler! My roommate and lead singer of
Given that this is the first time the family meets Chandler, I'm guessing this is Ross and Chandler's first year or even semester in college. If not, this means he had a roommate for a lot longer and he didn't mention at least a name to his parents.
Ross: So I’m thinking about asking Rachel out tonight. Y'know maybe
play her that song we wrote last week.
Chandler: Emotional Knapsack?
The next flash back happens in The One where the Stripper Cries:
Note: Ross and Chandler are at a Class of '91 reunion
Flashback, Year 1987
Ross: Hey. Hey, check out the flyers for the band. I made 'em on a
Macintosh in the computer room!
Chandler: Awesome, the name really stands out.
Ross: Thanks to a little something called "Helvetica Bold 24 point"!
The One with all the Thanksgivings:
They remain friends and room mates, and again Chandler is invited to Thanksgiving, only this time Monica is thin.
The One With the Sonogram at the End:
The first appearance of the museum.
Museum of Prehistoric History, Ross and a co-worker (Marsha) are
setting up an exhibit which includes some mannequins of cave people
Assuming the air date is also the same date in the episode, and that the museum requires a Ph.D to work there, it takes place in 1994.