At a certain time each week, in about 5 mins I think, everyone posts memes or notes and then we zap everything we see pop up. It's to stress test Lightning wallets.

Connect a Lightning wallet, such as Wallet of Satoshi, and people can zap you.

From my understanding, this are 30 min of stress testing the lightning network. Every participant is sending zaps to any post using the #zapathon tag. it's every Thursday and Friday at 22 UTC (23 Europe)