Not sure the exact age, but it’s xkcd 1288, they’re up to 3195 now, and they’re usually posted every Monday Wednesday and Friday.

Napkin math says roughly 12 and a quarter years ago. (3195 - 1288 for total comics since, / 3 for number of weeks since, / 52 for number of years since, gets you 12.22 ish)

There’s some slightly more recent ones that are still many years old:

1625: Image

And 1697: Image