BART announced in celebration of BART’s upcoming 50th anniversary on September 11, BART is offering a 50% discount on Clipper fares for the
entire month of September 2022.
The reduced fare will be automatically deducted when using Clipper at the fare gates.
BART also announced various festivities for its anniversary, including stuff for sale.
Details at:
https://www.bart.gov/news/articles/2022/news20220811