I call whenever I feel like it - why have rules for this sort of thing?

If someone thinks I'm overeager, well, fuck them - they're apparently not into me anyway. If the spark is gone after some time, then it probably wasn't strong enough in the beginning anyhow.

So call whenever you feel like it. If your date likes you, there's no such thing as wrong timing, and if your date doesn't like you, it's better to get rid of them sooner rather than later.