This has probably been asked before, but this is a huge thread...
How do we square:
"25 BSF, October 31: Harry is born."
and:
"0 ASF, March: Storm Front. Harry is 25, according to Jim, and he's been wizarding professionally for two years. We can reasonably place the year 0 in the timeline within a year or two of 2000, and there's a fair amount of evidence indicating that it could be 2000."
with:
"AGE 27-28: Storm Front" ?
I'm in favour of the first two, since making him 25 in 2000 is easier for me to remember and calculate from, as we'd share the birth year 1975.
I've usually gone with the context of placing Harry just about a year younger than Jim. I don't know (textev) if that's accurate but it would give Jim the advantage of being also being within a year or so of the same age as Harry during the writing months. In March 0 ASF, that would set Harry at a few weeks less than 25-1/2. (Yes, I know that sometimes Jim has gone back to set a shortie in an earlier time setting, such as Irwin Pounder's earlier years, but Harry's own timeline in the books seems to roughly echo RL time.)
There can be advantages to writing an urban fantasy character who has seen about as much of the wider world and contemporary events as the author. When one is twenty, there's more of a stretch to make a seventy-five year old character's ideas and outlook, or a three year old's, be consistent with what it's like to really be that age. Often it's done, and very well, but it's just a bit more intentional. When one is twenty-five and one's friends and peers are about the same age, that's a constant reality check. My experiences, my norms, are effectively considerably different than are those of someone far older or far younger. We've grown up in different worlds, because of time and events we've experienced.
For my guesstimate that JB 26 Oct 1971 would parallel Harry Dresden 31 Oct 197x,
Storm Front was written during his coursework with Debbie Chester at OU, Norman, Oklahoma.
Storm Front was published in 2000, but SF and FM were ready and I think GP also finished or nearly so, by the time SF hit the shelves. From that, I'd guess that Dresden's birth year would be more in the 1971 to 1974 range rather than all the way to 1975. Just guessing.