The timing of transferring to another school is basically the start of classes. The football player will want to leave their former school before classes start, so he can start his "transfer" clock of sitting out one academic year. UNL starts classes for Fall 2014 next Monday, August 25th. That player will also want to transfer to his new school before their academic year starts, so he can take part in their fall practices. For schools that use semesters (like NU) that Fall semester will begin this week or next week. Some schools will use "quarters" for their academic year, and their Fall quarter won't start until mid-to-late September. I remember when Richie Incognito was kicked off NU late in Fall Camp, his transfer options were limited because school had started for most colleges. He decided to transfer to Oregon, since their Fall Quarter started in late September. Of course, Richie didn't last long when he got to Eugene.