I've always thought that to use the month in a sentence you must use it with a preposition, such as "... at January"． But I saw a sentence in a press release today:

＂Nearly two-thirds of New York restaurants could be out of business as soon as January without some sort of additional government aid, according to a new study＂.

In this sentence "January" is not used with a preposition (e.g., "at January"), but instead with the phrase" as soon as ".

Why is this?

Can I use "as soon as at January" or "at January" instead of "as soon as January" in this sentence?