Every developer hits the same wall: your logs, your API responses, and your database rows all store time as a Unix timestamp — a number like 1785650000 that means nothing at a glance.
What a Unix timestamp actually is
A Unix timestamp is the number of seconds since January 1, 1970 (UTC). It's the de-facto standard because it's simple, timezone-agnostic, and trivially comparable — but human-unfriendly. 1785650000 could be any date in any timezone until you convert it.
The conversions you'll actually need
Timestamp → date: the one you do 10 times a day when reading logs or debugging an API. 1785650000 → 2026-08-02 12:53:20 UTC.
Date → timestamp: needed when you're querying an API with since=/until= params, or seeding a database.
Timezone awareness: a timestamp is always UTC under the hood — the display is what changes. A converter that ignores timezones will silently show you the wrong time.
The trap most people fall into
Milliseconds vs seconds. Some systems (JavaScript Date.now(), most ORMs) use milliseconds; Unix time is seconds. Off by a factor of 1000 means a date in 1970 — or in 50,000 years. Always check which unit the API expects before you paste a value.
Do it in seconds, in your browser
I built a free timestamp converter that does all of the above — seconds and milliseconds, both directions, timezone-aware, no signup, nothing uploaded to a server:
👉 https://tooly.work/tools/timestamp-converter.html
(Adapted from my Unix timestamp converter guide. Tooly has 57+ free browser tools — no signup, files never leave your device. Founding deal: 20% off Pro forever until Aug 31, 2026.)
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