What date formats can I type besides a raw number?

Anything JavaScript's own Date constructor can parse. ISO 8601 (2026-06-11T14:32:00Z) parses reliably everywhere, and looser strings like June 11 2026 usually work too. That looser parsing isn't governed by a real standard, so an ambiguous format can be read differently across browsers, ISO 8601 or a raw Unix number are the only fully safe bets.

Does the "3 hours ago" relative time freeze once it's shown, or keep updating?

It keeps updating on its own: the tool re-evaluates that label every 30 seconds so a tab left open doesn't drift out of date, while the timestamp you entered and the other converted fields stay fixed to whatever you typed.

Why does the tool accept a negative number as input?

A negative Unix timestamp is a legitimate date before the epoch, January 1, 1970: -86400 is December 31, 1969. The parser accepts a leading minus sign for exactly that case instead of treating anything below zero as invalid.

Unix Timestamp Converter: Epoch to Date & Date to Epoch

What is a Unix timestamp?

A Unix timestamp counts the number of seconds elapsed since January 1, 1970 at 00:00:00 UTC, also called the Unix epoch. It is timezone-independent: 1749649920 refers to the same instant everywhere in the world, regardless of local time.

This makes it ideal for storing dates in databases, logging events, and computing time differences without timezone confusion.

Seconds vs milliseconds

This tool auto-detects: if the number is larger than 1 000 000 000 000 (13 digits), it's treated as milliseconds; otherwise as seconds.

SecondsMost Unix systems and APIs, JWT exp/iat claims

MillisecondsJavaScript's Date.now() and most browser APIs

NanosecondsNode.js performance timers

Common use cases

Backend developers use Unix timestamps in JWT exp claims to set token expiration, in database records for created_at and updated_at fields, and in logs for unambiguous event ordering.

Frontend developers convert timestamps to local strings for display and compute relative times ("3 hours ago") for activity feeds. The ISO 8601 format (2026-06-11T14:32:00Z) is the standard for APIs and is sortable as a string.

Frequently asked questions

Anything typed as pure digits (with an optional leading minus) is compared against one cutoff: 1,000,000,000,000. Below it, the number is treated as seconds; at or above it, as milliseconds. That split holds up in practice because a seconds-based timestamp won't reach 13 digits until roughly the year 33,658, while a milliseconds-based timestamp for any recent date already exceeds it.