I understand that it means the same thing. In Spanish and in French, A is used in this sentence. Even if UNTIL means the same, the word to translate is A. hasta is also used in Spanish and jusqu'à in French. What I mean is, when I'm learning, I prefer make the translation that I see, and the rest will come later, when my Spanish comprehension will be better.
Duolingo would not be the place to try to figure out all the nuances of when to use which. It isn't a simple answer.
http://spanish.about.com/od/prepositions/a/de_vs_desde.htm gives a pretty good introduction to these words, although he will probably still leave you a little uncertain. In almost every situation, one is usually the correct to use; however! this is one of the situations in Spanish where the incorrect is still sometimes used by some speakers.
I do urge you to try to learn this though, because there are a few times when using the wrong one completely changes the meaning.
Fun fact: September, October, November and December were originally the 7th,8th,9th and 10th months, respectively, of the pre-Julian Roman calendar, and were named after the latin words for 7,8,9, and 10. The julian calendar inserted January and February into the lineup and bumped the other months out of their position.