On November 10, scheduled push campaigns stopped going out for 3 hours and 48 minutes (1:40 p.m. to 5:28 p.m. UTC)
A routine update changed the way a date was written in the handoff between the system that holds scheduled campaigns and the system that releases them. This caused some of the campaigns scheduled to be sent in the impacted window to fail.
The engineering team reversed the update, and scheduled pushes resumed at 5:28 p.m. Campaigns still inside their send window at that time went out.
Future mitigation: We now verify that date format is properly set up, and that a campaign send is functional before this kind of change goes live.