The race began life as a 5 day race in 1985 before becoming the 7 day race in 1988. In 1996 Sri Chinmoy was inspired to make it a 10 day race and in 1998 a 6 day option was also added. The 10 day and 6 day began their lives on Wards Island in Manhattan before switching back to Flushing Meadow in 2002.
Six day races take a substantial investment in time and effort and the New York events are no exception. Unique on the multiday calendar, the Self-Transcendence 10 day is the only 10 day in the world and the 6 day is the oldest such event currently taking place.
http://us.srichinmoyraces.org/events/6-day-race
Here is a list of 2012 6 day race dates of which I am currently aware. The Trans-Britain is different in that it’s a stage race as opposed to a non-stop race like the others.
29/03/2012 GRE International Ultra Festival http://dayrunners.gr
22/04/2012 USA Self-Transcendence 6 day http://Srichinmoyraces.org
09/05/2012 HUN UNIX 6 Day/48 hour http://www.unixsport.hu/hatnaposfutoverseny
03/06/2012 FRA Antibes Ultra Festival http://6jours-antibes.fr
08/06/2012 DEN Bornholm 6 Day 48/24/6 http://6-24-48-timer.dk
30/06/2012 ITA Pantano 6 Day Race http://www.6giornidelpantano.blogspot.com
08/09/2012 GBR Trans Britain http://gobeyondultra.co.uk