cut the Alduin Akatosh crap everyone, and lets try to explain to the OP why the dragons are not our friends anymore.
Except that may potentially hinge on the relationship of Alduin/Akatosh, no?
Not mentioned as a god of time. Having an effect over time does not Akatosh make. We already know the dragon language can affect time, so does that mean all the dragons and anyone that can use thu'um are all split personalities of Akatosh? Man, Akatosh needs some psychiatric help....
It's overstepping to try to compare the place Alduin occpuies in the nordic faith to the individual dragons and thu'umers. They don't have a declared position in the Nordic pantheon, and they are therefore hyperbolic. Even if we don't accept right away that Alduin is a God of Time, let's merely take a look.
I think it's pretty obvious that quite a bit of TES is about the repetition of themes, particularly noticeable when it comes to that which the different races revere and worship, or at least admit as a force to be reckoned with. And every race would appear to have a place allotted for Time. Now, for our Nordic pantheon (not necessarily limited to Aedra), from http://www.imperial-library.info/content/morrowind-varieties-faith-empire, we have: Alduin, Dibella, Orkey, Tsun, Mara, Stuhn, Kyne, Jhunal, Shor, Ysmir, Herma-Mora, Maloch
I think we can agree to rule out Herma-Mora as being the rep for Time, as we can for Shor and Ysmir.
For the rest, namely Dibella, Orkey, Mara, Stuhn, Tsun, Kyne, Jhunal, and Maloch, wouldn't you at least agree that these names sound varyingly similar to Dibella, Arkay, Mara, Kynareth, and Malacath, with Stuhn and Tsun being arguably construed as Stendarr and Triminac?
And even if you won't agree to that, out of that whole list of Nordic gods listed, Alduin is the only one we have any information for whatsoever to indicate any dominion whatsoever over Time.
At this point, it's again merely occam's razor to indicate that Alduin, whose name is similar to Akatosh/Auriel/Alkosh/Akal, who is a Dragon like Akatosh/Alkosh, and who has an indicated dominion over time, would be the Time God for that pantheon.
Trying to construe it otherwise, to me, is actually working much harder. If I were to reverse the situation and ask you to procure a Nordic deity who would be more fit to occupy the God of Time slot, you would have nothing, and could only repeat, "well, we just don't know." There's very little that any of us "know," whether that be in lore or RL. It's the inferences that matter.