It depends how fast you run. A marathon is 26 miles and 385 yards.
2 hours 10mins
A marathon bar
For the personal challenge and satisfaction of being fit enough to run a marathon.
Wikipedia is a very valid source for finding out how long a marathon is. Specifically, a marathon is a long-distance run based around the 25 mile mark.
The first Boston Marathon was run in 1897 so as of 2016 it has been running for 119 year.
A 40k marathon is about 25 miles.
About 2-3 hours.