I understand that Ubuntu 12.04 LTS is the "long-term support" version and will have support until April 2017. While 12.10 will have support until April 2014, and fianlly 13.04 will only be supported until January 2014.

I'm just curious, how do the developers arrive at these dates, and at what point does 12.10 and, eventually 13.04, become LTS?

Thanks for your clarification.