User blog comment:The Milkman/Twitter Responses: Bethesda Still Having Issues/@comment-85.29.108.218-20121010083903/@comment-4113369-20121013203627

@The Iron Draugr

It depends on pronunciation, not spelling. The pronoun for "year" is "a" because it's pronounced like it begins with a "j". The opposite reason is why "hour" gets the pronoun "an". There aren't really any words where using either is fine (as far as I know), at least not when writing. Oral grammar is somewhat looser than written grammar, thanks to the variety of dialects, sociolects & accents widespread languages like English have.

Having English as your second language has its advantages :D