http://www.autosport.com/news/report.php/id/102912

2013 FIA World Endurance Championship

April 14 Silverstone 6 Hours (GB)
May 4 Spa 6 Hours (B)
June 22/23 Le Mans 24 Hours (F)
August 24 Sao Paulo 6 Hours (BR)
September 22 Austin 6 Hours (USA)*
October 20 Fuji 6 Hours (J)
November 10 Shanghai 6 Hours (PRC)*
November 30 Bahrain 6 Hours (BAH)

Notice anything missing? Something that lasts 12 hours in Florida?

At least I think the date don't clash, so maybe the OEM will see Sebring being important enough to run. I like how their excuse is that its cheaper this way. When their 2nd half of schedule is still all over the world...

Not holding my breath to any international ties for the new Grand Am/ALMS series in 2014, but at that point I think a good chunk of it is not actually NASCAR's fault...