A proposal to define a limited number of annual time windows in which network upgrades (aka hard forks) should be performed within. Policies for scheduling network upgrades outside these windows are also described.
View the full EIP - https://github.com/ethereum/EIPs/pull/1872
Note: The selection of the third weeks of January, April, July, and October are a starting point and I am not set on those being the dates. I am more interested in dates being defined.