okay I've seen a few people in various places saying Tim was 15 during Knightfall (and tangentially, since it happened during Knightfall, that he was 15 when he got his early driver's license, too), and no. he was still 14 lol. but I had to go on a bit of a rabbithole to prove it to my own satisfaction
setting aside for a moment the most straightforward way to calculate it (he's 13 in ALPOD and Knightfall happens less than four real-world years later, there isn't time to fit two birthdays in and have him be 15 already) because that's too easy, let's see, what actual panels can we look at here--
hm. I went to pull the ones where he gets his early license, but nope, they don't actually put his age in there:
Tim: YES! It's my driver's license! I forgot all about it.
Mrs. Mac: Driver's--? How can that be, you not being sixteen yet, an' all?
Tim: It's a special license. Dad signed a form that allows me to have it because of his handicap. I am mobile.
- Detective Comics #668
all we get explicitly is that he's not sixteen š¤
okay, wait, how about this!
Tim!Robin (narrating): Battling evildoers would be a lot easier if I had a driver's license. But that's two years away.
- Robin II: Joker's Wild #1
I initially went aha, this is way more clear-cut, driverās license is at 16 and heās two years away from that so he's 14 - but no, this could also be ambiguous because if you interpret Gotham as being in New Jersey (not necessarily the case! certainly not confirmed canon, but a fairly common placement), then apparently the age to get your NJ driverās license is 17, and itās the learnerās permit thatās at 16. so that could still point people at 15
also in Robin II: Joker's Wild #1, we have confirmation that Tim is in 9th grade at Gotham Heights High School, and that winter has also just started, so it's only a few months into the school year:
Tim: Gotham's expecting a cold winter. || Ives: You think they'd make people evolve before they let them into ninth grade.
unless we're arguing that somehow a full school year passes in the year-and-a-half of real time between publication of Joker's Wild (Dec 1991) and Knightfall (May 1993), he's still in 9th grade throughout Knightfall
how do we know he's 14 all throughout 9th grade, and not 15 at any point? well, for one thing, his birthday is July 19, so if he'd turned 15 before going into 9th, that would mean he'd turn 18 in the summer before 12th, and therefore graduate high school just before his 19th birthday. not out of the question for kids in the U.S. school cycle, depending--but we know it's not the case for Tim in particular. he was confirmed in Red Robin to be 17, not 18, during senior year.
he dropped out of 12th to go on Brucequest:
Tim: [...] Things got a bit...hectic...in my life...
Ives: Enough to keep you from coming back to high school--but who needs a diploma when you're a rich gossip page regular?
Tim: Give me a break... So, how's senior year been?
- Red Robin #17
and it's a major plot point that he was still a minor at the time, hence needing the emancipation to thwart Ra's plans for Wayne Enterprises:
Tim (speaking to Ra's off-screen): Two things happened today, Ra's. The first is that I became an emancipated minor.
- Red Robin #12
so! definitely 17 during 12th grade, definitely 14 during 9th. which is when Knightfall takes place and he gets his early driver's license.