The ranking system for our clan is based on time. This is because true skill cannot be accurately judged due to a lack of kill/death ratios, screenshots, etc. I do not use the Halo ranking system at all as it is, too, based off of credits, not actual skill. So here is the lineup of ranks as well as time required to obtain them:
***NOTE***
Time period STARTS with the promotion to the following rank. For example, you must serve 2 weeks STARTING when you are promoted to Private in order to obtain Pvt. 1st Class
Grunt - 1 week recruit period
Private - Obtained after 1 week recruiting period
Private 1st Class - Obtained after 2 weeks of satisfactory service
Specialist - 3 weeks
Sergeant- 1 month
Staff Sergeant - 1 month
Sergeant First Class - 1 month
Master Sergeant - 6 weeks
First Sergeant - 6 weeks
Sergeant Major - 6 weeks
Command Sergeant Major - 6 weeks
Sergeant Major of the Army - 2 months
Warrant Officer - 6 weeks
Warrant Officer Grade 2 - 6 weeks
Warrant Officer 3 - 6 weeks
Warrant Officer 4 - 6 weeks
Chief Warrant Officer - 2 months
2nd Leuitenant - 2 months
1st Leuitenant - 2 months
Captain - 3 months
Major - 3 months
Leuitenant Colonel - 4 months
Colonel - 4 months
Brigadier General - 6 months
Major General - 6 months
Leuitenant General - 1 year
General - 2 years
GOA - Never... I'm IT