Timestamp Converter

Unix timestamps — also called epoch time — measure time as the number of seconds elapsed since January 1, 1970 at 00:00:00 UTC (the "Unix epoch"). This format is ubiquitous in software: database records, API responses, log files, JWT tokens, HTTP headers (like Last-Modified), and cryptographic signatures all express time as a Unix timestamp rather than a human-readable string, because numbers are unambiguous, timezone-agnostic, and trivially comparable.

There are two common variants: seconds (a 10-digit number like 1741618800) and milliseconds (a 13-digit number like 1741618800000). JavaScript's Date.now() always returns milliseconds. Most Unix/Linux system calls and POSIX APIs use seconds. Databases vary — PostgreSQL stores timestamps with microsecond precision while Redis typically uses seconds or milliseconds depending on the command. This tool auto-detects which unit you're using based on the magnitude of the value.

Converting between timestamps and human-readable dates is more subtle than it appears, because the same Unix timestamp represents different local times in different timezones. 1741618800 is 15:00 UTC, but that's 10:00 AM in New York (ET), 16:00 in Paris (CET), and 00:00 the following day in Tokyo (JST). For this reason, ISO 8601 — the international standard format — always includes a timezone offset (like 2025-03-10T15:00:00Z for UTC, or 2025-03-10T10:00:00-05:00 for Eastern Time).

When building APIs, always store and transmit timestamps in UTC, and convert to the user's local timezone only at the presentation layer. This tool handles both directions: paste a Unix timestamp to see all its human-readable equivalents, or pick a date, time, and timezone to get the corresponding Unix value. Section 3 shows the current timestamp updating live every second, useful for quickly grabbing "right now" as a Unix value.