A friend and I were debating recently the proper classification of the word "nearly" in the following sentence: "I was studying until nearly dawn." We both thought it was an adverb modifying "until," which was modifying "studying." But he was more convinced than I was, and I'm still not sure. Rearranging the syntax makes the word's adverbial qualities more clear, but it also changes the meaning of the sentence (if only subtly). Could somebody clarify exactly what the word is doing in the sentence above?