Events such as this are announced via the P2Pool-notifications mailing list .
P2Pool is a decentralized Bitcoin mining pool that works by creating a peer-to-peer network of miner nodes.
As opposed to usual pools, P2Pool helps to secure Bitcoin against double-spending and 51% attacks. P2Pool's initial setup requires a little more effort but provides equivalent payouts with a higher variance and no need for trust in a pool operator.