GG5, 中辞典

I'd keep it, if only because the JEs have it.
Yes, better to have the more internationally understood gloss first, but I don't think there's any need to go around re-ordering things on those grounds.

I agree that "two weeks" should lead but is this entry even needed? I don't think it's necessary to have a Japanese translation for "fortnight". Anyone can work out that "two weeks" is "2週間".

My intention was to place the more "universal" [0] gloss first. At least in my understanding, "two 
weeks" isn't strictly AmEng. This is also how gg5 has it (which doesn't mark "two weeks" as 米, but does 
mark "fortnight"). I think we can agree that the order of our glosses matters, even if we don't agree on 
the particular.

[0]: http://www.edrdg.org/wiki/index.php/Editorial_policy#Meanings: "make the translations as 
international as possible."

The main reason fot having this as an entry in 
the first place is that "fortnight" isn't a 
straightforward translation, isn't it?

So the first gloss has to be the preferred AmE term? I would have thought having both would be enough.