TLS Certificate Expiry: Detection, Renewal, and the 47-Day Future

The cert expired on a Saturday at 02:14 UTC — not a Tuesday, not during business hours. That's when I learned our paging rotation had a gap between outgoing and incoming on-calls. By the time we deployed a valid cert, we'd lost 97 minutes of checkout traffic and two SOC 2 evidence items. TLS certificate expiry is the most predictable outage in production infrastructure, and it's about to get 8x noisier as validity periods drop from 398 days to 47 by 2029. This guide covers what expiry means at t