In bjj, it's based on your improvement, for lack of a better way to say it right now. For instance, a white belt wouldn't even be considered for a blue until he can hang with and go head up with the blue belts. If that takes you two years, then guess what? you will get it in two years when that's been accomplished. I like this method, as it ensures that you actually know how to apply what you are learning.
In judo, it's based on several things - it varies from state to state I believe, but the guidelines are likely about the same. There's a point system - you get points for going to class, you get points for competing - when competing, you get more points if you beat someone of a higher rank than you. Also, you have certain techniques that are required knowledge for certain belt levels. If you've fulfilled all of the requirements and your instructor feels you deserve it, you may test. The above rules apply up through brown belt. to get your black belt, you have to test in front of the state judo board, and they have to deem you as deserving of a black belt. I like this method also, but like the way we do it in bjj better.
When I was in longfist, it was like it was when I was in karate. There are set techniques/principles/forms that you must know, and as you progress, you have to demonstrate your competency at applying them. I like this method least of the three mentioned.
i'm nobody...i'm nobody. i'm a tramp, a bum, a hobo... a boxcar and a jug of wine... but i'm a straight razor if you get to close to me.
-Charles Manson
I will punch, kick, choke, throw or joint manipulate any nationality equally without predjudice.
- Shonie Carter