My sister and I were arguing about the proper (grammar-wise) birthday greeting when saying it in advance. Both of us were wrong so I won’t be discussing the dirty details of our debate because those would just make us look passionately stupid. Here’s the best analysis I have read:

You Ask: Is it correct to say “Advanced Happy Birthday” or “Advance Happy Birthday”? Or should I just say Happy Birthday in Advance?”

Grammar Pulis Answers: Hmm, I am so used to saying Advance Happy Birthday, so I never really wondered about its grammatical soundness. Until now.

Let’s analyze. 

First, let’s consider the meaning of both words, advance and advanced. Both can be used as adjectives. There are, however, slight differences in the usage.

Dictionary.com says that advance is an adjective that describes something that is given, made, or issued in advance. A couple of examples are: advance payment and advance copy.

Advanced, on the other hand, is an adjective for describing something that is further along in progress or something enlightened. For example, Advanced English Program, advanced theories.

Based on the definitions, it would seem then that the former is more appropriate than the latter.

BUT, this requires more analysis. The second thing we need to look at is what the word advance is modifying. If we say that it is modifying the word birthday, then that does not make sense because the birthday is not advanced. The one that is being given in advance is the greeting. That means then that both Advance Happy Birthday and Advanced Happy Birthday are grammatically wrong. So, you really are better off saying, Happy Birthday in advance. Or just say, Happy Birthday.

Personally, however, I wouldn’t mind it so much if anybody says Advance/Advanced Happy Birthday to me. I mean what kind of rude, grammar-obsessed person would I be if I slapped a grammar violation fine on a person who is being nice to me?

As the Grammar Pulis, I would let something like this nonstandard usage slide, then I’ll smile, and just take the gift that goes with the greeting. 

Source: http://grammar-pulis.blogspot.com/2009/04/you-ask-grammar-pulis-answers-advance.html