Before starting to date (in the sense of “go out, do things, have fun, and get to know each other”)? I’ve gone out on blind dates, which I guess is “zero amount of time.” I’m not even sure why there would be a rule about this. Just be safe, and if it’s someone you don’t know too well, stick to public areas (like restaurants) and let someone else know that you’ll be out and when you plan to be back and you should be fine. Have fun, be smart.
If by “date” you mean “begin an exclusive relationship with this person, forsaking all others,” I might wait until that seems right or feels comfortable for both of you, but that doesn’t happen like clockwork all the time. Also, I see a difference between “dating” (which you can do with as many people as you have time and inclination for) and what they used to call “going steady,” which is a lot more exclusive and usually includes they words “boyfriend” and/or “girlfriend.” I understand that these days, people often see these as the same thing, i.e., if you go out on a date with someone, it means that you’re not dating anyone else, no matter how casually.
At any rate, timing is usually more of an organic thing with me. There’s no such thing as relationship tenure if it doesn’t feel right, no matter how long I’ve known someone. It’s not like they have a “date by” date; no alarm goes “ding!” to tell me they’re ready. It would be a lot easier if they did!