Understanding Unix Epoch Timestamps & Timezones

Unix timestamp (Epoch time) tracks absolute time as an integer representing elapsed seconds since **January 1, 1970 00:00:00 UTC**.

1. 10-Digit Seconds vs. 13-Digit Milliseconds - **Unix Seconds (10 digits):** Standard POSIX timestamp format used in Linux systems, Python `time.time()`, and databases like PostgreSQL. Example: `1700000000`. - **Unix Milliseconds (13 digits):** Precision format used by JavaScript `Date.now()`, Java `System.currentTimeMillis()`, and MongoDB ObjectId timestamps. Example: `1700000000000`.

2. ISO 8601 & UTC Standardization Storing raw Unix timestamps avoids timezone ambiguity in global applications. Convert to ISO 8601 (`YYYY-MM-DDTHH:mm:ss.sssZ`) at application boundaries for human readability.