Depends what you need to recover from.
If you ride with a power meter, you use it to measure how much effort you're capable of, and then each time you ride you compare the effort from that ride against your personal limit to get a pretty good estimate of how much stress you took on. That gives you a reasonable time frame: you'll be recovered tomorrow for this much effort, but it'll take two days for that much.
You can get recovery estimates from a chest strap HRM and good software, too.
I'm beat for a couple days after a long climb. A weekend ride is usually easier and I'm mostly ok the day after. Evening week day rides usually take less than a day.