After weeks of increasing anticipation among students, Flunk Day 2016 finally arrived on Tuesday, May 10.

Despite scattered showers overnight and early Tuesday morning, the rains had mostly stopped by 6 a.m., as the bells atop Old Main began to ring and Flunk Day friars took to the grounds to rouse their classmates.

As students moved out toward the South Lawn, they encountered a velcro wall, an obstacle course, a rock wall, and a track where participants were closed into giant hamster balls before racing one another. Additional activities were rolled out throughout the day, including a tug-of-war and a faculty-student softball game with special guest star Abraham Lincoln.

The evening concluded with Glow Rage, where participants spattered each other with glow-in-the-dark paint as DJs blasted electronic dance music.

See a Storify of highlights of Flunk Day—Knox's traditional, surprise celebration of spring.

Flunk Day officially began in 1922, but student-organized spring festivals on the Knox campus date back to the beginning of the 20th century. Though its exact date each year is always a closely guarded secret, it has now taken place on a Tuesday 11 times since 1986—more than any other day of the week.

See more Flunk Day pics on Flickr.