From what I can understand there are certain codings that correlate to the banned date. Would it be possible to get a quick list from Riot so we can better inform the player base? As with all bans if you have a question please contact Player Support which is located here: https://support.leagueoflegends.com/...s_requests/new We the player base can only do so much. Riot has the ability to answer your questions about a ban and possibly fix the issue with your input about the situation.
Example:

2100 - Account Security Compromised(no Red post to verify)

2103 - Inappropriate Name Ban(no Red post to verify, but here is a link to two of the threads)
http://na.leagueoflegends.com/board/....php?t=3122042 http://na.leagueoflegends.com/board/....php?t=3124627

2106/2107 - Billing Issue
http://na.leagueoflegends.com/board/...php?p=32291540

2200 - Refer-a-Friend program Issue(no Red post to verify, but here is a link to one of the threads)
http://na.leagueoflegends.com/board/....php?t=3371867
http://na.leagueoflegends.com/board/...43243#27743243 (some red verification, but no straight out answer)

2212 - Temporarily locked - Account under investigation
http://na.leagueoflegends.com/board/...php?p=31590143

2222/2223 - Charge-back suspensions
http://na.leagueoflegends.com/board/...95243#16195243

2286/2287 - Common Toxicity Ban
http://na.leagueoflegends.com/board/...86134#31586134

2400 - Impersonating "Riot" with thier name --No Red post to verify.--
http://na.leagueoflegends.com/board/...3#post36797693

2499 - Serious Disciplinary Action(Not Tribunal related) --May be account selling/sharing, but no Red post to verify.--
http://na.leagueoflegends.com/board/...41921#33841921

3333 - Unknown ban.--No Red post to verify.-- Links contains a screenshot to the ban.
http://na.leagueoflegends.com/board/...2#post37150842
http://na.leagueoflegends.com/board/....php?t=3378574

If anyone has links to other dates from a Red poster, please share and I will update this list. It would also make it much easier if Riot could post a listing also.

**EDIT: The years may have been moved up by 1 since it is now 2013. So if someone was banned until 2287 it may still be related to the Common Toxicity Ban.**

Updated 2035pm CT 5/23/2013

Found a few more, updated.

2499 is one they are using. Happened to me. I'll update you once I know what tis for.

For now put it as "Severe ToS Violation"

This is a good thing to sticky when we get what the "2499" thing is. A lot of people ask "I was banned until - What does that mean?!" It will clear up questions when people are "permabanned for no reason!"

My ticket was just picked up by an unkown rioter. I should get an answer soon.

Still looking for more ban dates.

Might want to add that this forum is only used for discussing 2286 bans, all those are bans aren't discussed on the forums.

2499 = Account sharing or selling.