How long do you wait to call?

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If someone gives you their number how long should you wait before you call them?

See, I would normally think like 2 or 3 days so as not to seem like an eager, desperate freak. But this girl gave me her # yesterday and asked me to call her so we could go for a drink this weekend. I didn't call her today though because it's the very next day... but now it's like 11pm Friday and I'm thinking I should have. Wtf!