100 Days of Running is a fitness movement which started in 2015 to encourage people to make running a part of their lives, a habit, and a way towards better fitness. The 2020 edition starts on Apr 25th and will have more than 50,000 runners across India and indeed from across the world commit to run daily through 100 days of summerâs hottest months. This event is the largest such multi day challenge in the world.