Unix Timestamp Guide: Seconds, Milliseconds, and Time Zones
Avoid common date bugs when moving between logs, APIs, and user-facing timestamps.
Last updated: May 4, 2026
Seconds vs milliseconds
10-digit values are usually Unix seconds, 13-digit values are milliseconds. Mixing them is a top source of date bugs.
Store UTC, render local
Keep canonical timestamps in UTC and convert to local time only for user display. This prevents daylight-saving and server-region drift issues.
API contract tip
Document timestamp unit explicitly in API schemas. Never rely on consumers to guess seconds vs milliseconds.