It's my crush's birthday, how and when should I tell him happy birthday via text message? Help?

So this guy I like (But he doesn't know I like him, I think!) his birthday is tomorrow. I won't be seeing him until Friday for his party though. So should I text him and tell him happy birthday? What should I say, I want to keep it simple. Also when should I do it. Should I text him from tonight and keep the conversation going until 12:00 or should I text him later on like lunch time?
It's my crush's birthday, how and when should I tell him happy birthday via text message? Help?
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