https://www.mercurynews.com/2020/01/12/19th-annual-no-pants-bart-ride-day/

Today about 40 people braved the cold temperature and participated in the 19th Annual “No Pants” BART Ride Day on Sunday, Jan. 12, 2020. Participants from around the Bay Area gathered at several meeting locations and boarded BART trains and meet up in San Francisco. They then exited the stations and paraded in their underwear to city hall for a group picture. After the group photo many of them decided to a visit a local bar to have drinks and food.