If I'm reading things right, I guess this must mean that time is supposed to run at a different pace in our world than it does in Amestris. This is what I'm talking about ...
1910: This is when Ed and Al leave home; Ed is 12 and Al is 11.
1913-4: This is when the main events of the anime must take place, in order for ages to match up. Ed is 15 (his birthday is in the winter, I guess he would have turned 16 until the end of 1914) and Al is 14.
September 2nd, 1916: This is when episode 50, Death, takes place -- at least in OUR world. That's the date mentioned in the preview for 50, and on that day, just as shown in the series, German zeppelins bombed London (and one zeppelin was shot down -- the one that killed Alter!Ed). (More info on that here). So unless a lot more time goes by in the course of the series than it seems, and Ed is older than we think, then there's a difference in years when Ed comes out on the other side of the Gate.
Now, here's where it gets weird. During Schiezka's narration sequence, it's clear that not much time has passed (I believe she says one year? Wiki says only a few months, but I don't think that's true). So it should be 1915 (?) when Al (now 10 again, or maybe he's just turned 11) goes to train with Izumi again.
However, when we see Ed in Munich it is 1921. Maybe these two scenes aren't actually supposed to take place at the same time -- though honestly, I want to believe that Ed and Al are riding on those trains thinking of each other at more or less the same moment! ;). However, even so, that's a difference of six or seven years. The means that in the movie, Ed would have to be, like, 23 or 24 years old. Which I don't think he is.
So basically, I think that time in Amestris is supposed to go slower than it does in our world. Presumably, when Ed came through the gate a second time, several years had passed by -- it was probably around 1919.
Actually, if you take the Kids OVA into account, I think it must have been 1920 or so when he appeared again in our world -- because it's stated there that he turn 100 in 2005, which would have meant he should been born in 1905 -- and he wasn't, he was born in 1898. The only way it works out really is if he's 15 in 1920. I don't know what age Al is supposed to be in the movie ... or even a period of time is stated as having gone by since the end of the series and the beginning of the movie in Amestris, I haven't watched it thoroughly enough.
Now don't ask me to explain why there wasn't a huge gap in time during Ed's couple hours back in Amestris during the movie. *acknowledges the abundance of plot holes in the anime, but loves it too much to care*
Please tell me if I've got any of these dates or ages wrong. *_*;; I almost hope I do.