An upgrade to address the difficulty bomb
The EIP is discussed in the hard fork meta: EIP-2387
An introduction and analysis of the difficulty bomb timing can be found here.
The fork contains EIP-2384, which delays the EIP by 4,000,000 blocks.
The fork is due to execute at block number 4200000, which will occur around December 31, 2019.
The countdown and upgrade status of nodes can be seen here