Pre-installation modification time is 2,099 years and so many years after the point of time, after installation choose a free trial for 30 days, and then quit idea, change the time back so that you can successfully register
If you have previously used an activation method such as an authorization server, do not eject the trial interface, go to the C:\Users\ computer user name \. Rename the Idea15.key file to Idea15.key.bak under the Intellijidea15\config directory
or use online activation:
Select "License Server" input when registering
http://idea.lanyus.com/
Click "OK" to activate directly without patching
Alternate activation server address:
Http://0.idea.lanyus.com
Http://1.idea.lanyus.com
Http://2.idea.lanyus.com
Original: http://blog.csdn.net/yipanbo/article/details/50612974
Go JetBrains Registration Code calculation (IntelliJ idea 15.0 registration code activation)