I have been working on a timeline of my own (by the way, great job ToTheNines!).
The timeline was holding up nicely... until I reach the episode Timing Is Everything.
At the beginning of the episode, we see that in
2105 the Post Office is celebrating its 200th anniversary. Don and Splinter get zapped back in time to the day when they mutated.
The problem is, when Donatello sends the letter to Raph and Mikey from the past, the Post Office is celebrating its 100th anniversary. Meaning that Splinter and the Turtles mutated in
2005 and Things Change takes place in
2020.
And that's not all. Leo and Cody get zapped to the day when the Turtles first defeated the Shredder. Cody checks the date and his screen reads
1993.
http://imageshack.us/photo/my-images...magineoxv.jpg/
I think that for my own sanity I'll pretend this episode never existed...