How long after a person's birthday can you call and still offer wishes (even belated)?
My answer: 2 days...3 if the birthday was on a weekend.
However, you must know the actual birthday.
This morning, my brother in law, Akiva, called and said, "Happy Birthday! Sorry, I'm late. I meant to call you on Wednesday."
"Uh, my birthday was last Saturday. Sorry, man, you don't get credit :-)"