SSL Certificate Expiry
Calculate the days remaining until an SSL/TLS certificate expires.
Inputs
Days before expiry to trigger renewal
Days Until Expiry
-222
Status
EXPIRED
Days Until Renewal Needed
-252
Renew By Date
2025-12-01
Step by step
Expiry date
2025-12-31
= 2025-12-31
Days remaining
expiry - today
= -222 days
Renewal deadline
expiry - 30 days
= 2025-12-01
Days until renewal needed
renewal_date - today
= -252 days
How it works
SSL/TLS certificates have a fixed validity period. When they expire, browsers show security warnings and connections may fail. Planning renewal before expiry (with a buffer for processing time and potential issues) prevents outages. Most CAs now limit certificates to 90-398 days.
Formulas
Days remaining
days = expiry_date - today
- expiry_date
- Certificate's notAfter date
- today
- Current date
Renewal deadline
renew_by = expiry_date - buffer_days
- buffer_days
- Lead time needed for renewal process
Frequently Asked Questions
What happens when a certificate expires?
Browsers display a security warning (often blocking the page), automated API clients reject the connection, and search engines may penalize the site. Some services like Let's Encrypt auto-renew, but any failure in that process can still cause an outage.
How much buffer should I allow for renewal?
30 days is a common minimum — enough time to notice renewal failures, resolve domain validation issues, and propagate the new certificate across load balancers and CDN nodes. Critical production systems often use 60+ days.