Canon Timeline
~~ Series 1 ~~
(All of these dates are taken from the BBC's version of John's blog, with a few additions from Molly Hooper's blog. There aren't any years used on the blogs, but I'm assuming 2010, just because it's easier.)
Late 2009? - John is wounded (shot in left shoulder), discharged from the military, and invalided home to England.
14 Dec 2009 - John's first blog entry. ("Nothing")
24 Jan 2010 - John meets up with "some of the rugby lads from Blackheath".
29 Jan 2010 - Mike Stamford introduces John to Sherlock Holmes.
30 Jan 2010 - John meets Sherlock at 221b at 7 o'clock, goes to a crime scene, gets kidnapped by Mycroft, goes on a stakeout, chases a taxi around London, observes a police drugs bust in his new flat, and shoots a serial killer to save Sherlock's life. And then they went for Chinese. [Ep01 - "A Study in Pink"]
07 Feb 2010 - John posts a blog entry titled "A Study in Pink".
23 Mar 2010 - John & Sherlock have a conversation in the comments on John's blog entry while they're both in the flat. (Notes: Sherlock has never see a James Bond film. Sherlock threatens to blow up John's cans of beer in order to get John to come downstairs and entertain him.)
23 Mar 2010 - John posts a rant about unmanned checkout machines. (And presumably, Sherlock & John go to a bank and take a new case.)
23 - 27 Mar - [Ep02 - "The Blind Banker"]
25 Mar 2010 - Molly Hooper posts in her blog that "Sherlock came in again tonight", blatently flirted with her, and left as soon as he got what he wanted.
26 Mar 2010 - "Jim from IT" comments to Molly Hooper's blog.
27 Mar 2010 - John posts an entry about breaking up an international smuggling ring and being mistaken for Sherlock.
28 Mar 2010 - John posts a blog entry titled "The Blind Banker".
28 Mar 2010 - Sherlock finds the "Study in Pink" blog entry and comments on it.
29 Mar 2010 - Sherlock goes to Minsk for a potential case, but turns it down. John posts an entry in his blog.
30 Mar 2010 - John comments to his 29 March entry: "Sherlock's back, Things are happening. New case. No time. Will write soon."
30 Mar - 06 Apr - [Ep03 - "The Great Game"]
01 Apr 2010 - Molly Hooper posts on her blog with a message for her missing boyfriend, Jim.
06 Apr 2010 - Molly comments to John's 29 March entry that her boyfriend Jim has gone missing. Harry and Sarah also comment because they can't reach John.
~~ Pre-Series ~~
Given the grammar school dates on his CV, John was 18 in 1999. That would make his birth year 1981 and make him 29 in 2010.
Using that timeline:
1999 - 2004 - Medical School
2004 - 2006 - PRHO (internship) & SHO (residency)
2006 - 2009 - Military service?
For various reasons, Jen and I decided Sherlock and John were 33 & 34 when they met. (Sherlock just turned 33; John about to turn 35.) That would make John's birth year 1975 instead.
Using that timeline:
1993 - 1998 - Medical School
1998 - 2000 - PRHO (internship) & SHO (residency)
2000 - 2009 - Military service?
(Not that it matters, but for reference sake, Martin Freeman was born in 1971.)