The fastest time to complete a marathon on each of the seven continents (male) is 21 days, 5 hours and 33 minutes, and was achieved by Wendelin Lauxen (Germany), from 31 October to 21 November 2012.

http://www.guinnessworldrecords.com/world-records/1/fastest-time-to-complete-a-marathon-on-each-continent-(male)