Understand Unix timestamps, milliseconds vs seconds, UTC vs local time, and common timestamp debugging mistakes.
Timestamp bugs can be surprisingly expensive because they hide inside logging, analytics, API payloads, and scheduled jobs.
The most common sources of confusion are simple: seconds vs milliseconds, UTC vs local time, and inconsistent formatting between services.
A Unix timestamp in seconds is much shorter than one in milliseconds. Mixing them up shifts the interpreted date dramatically, which is why this is one of the first things to check during debugging.