Time in Grade...

My 1st Dan certificate is dated 13 January 1983.
I tested in 1982 and did not receive this certificate until around April or May of 1983.

It is the date of  your certificate that is most often used to determine when you have met your minimum time requirements and are eligible for your next Dan promotion test/ranking.  Sometimes the date on your certificate is the same, or close to your actual testing date, sometimes it is not.

Different instructors, schools, organizations, and martial arts have different requirements with regards to "minimum time in grade" but most have some kind of requirement that is equivalent to either their current Dan ranking or next Dan rank, and some also include a minimum age.

It is important to remember that these are minimum requirements.  

Ideally, as you advance in rank you work on, improve, and bring up the quality of all your previous material, not just simply "add to" by learning something "new" as you advance.  Taking what you know already and making it better, or applying it in a new way, bringing the quality of everything you do up a level - that is what takes time. 

Respectfully,

Kathy Wiz

Here is the AAU's Dan levels AND combined training time:

Dan Level	Min. Time Between	Total Combined	Minimum Age
1st Dan	30 Months		8 Years Old
2nd Dan	1 Years	3.5 Years	10 Years Old
3rd Dan	2 Years	5.5 Years	13 Years Old
4th Dan	3 Years	8.5 Years	16 Years Old
5th Dan	4 Years	12.5 Years	20 Years Old
6th Dan	5 Years	17.5 Years	25 Years Old
7th Dan	6 Years	23.5 Years	31 Years Old
8th & 9th Dan	7 - 8 Years		38-39 Years Old

And here are the Kukkiwon's standard requirements:

(a "poom" rank is to designate a black belt under the age of 15)