Posted the same info in this thread a couple weeks ago but they finalized it today:

Basically this means that the latest an 8 game conference regular season can start is 2/27 for leagues with an even number of teams and 2/20 for leagues with an odd number of teams. That means practice will have to start up in mid-to-late January. It's far from ideal especially for schools in colder climates who don't have indoor facilities. You're also asking players to play up to 12 straight weeks (including the playoffs) in February-May and then come back in less than 3 months and start getting ready for another full season in the fall. This will impact the 2021 fall season due to injuries sustained in the 2021 spring season.

That said it's better than no season at all but the 2021 calendar year will present a ton of unique challenges to FCS teams that no program can adequately prepare for.