Does anybody know when the limits for the olympic games are announced and till when you have to brake them?

Answer 1

Your question is not clear. But if you mean "Olympic records" then they don't have to be announced, they are simply the best marks recorded during the Olympics, so you can only break them during the Olympics.
If you mean "Olympic standards", i.e. the performance an athlete must have to qualify for the Olympics, they are already announced (check with your National Federation) and any time is fine, but best before April 2008 when the so called "preliminary participant lists" are made by the National Olympic Comittees and sent to Beijing. I'd guess what it takes to qualify after that is maybe break the World Record or something...Hope that helps!