Unix Timestamp Converter — Convert Timestamps to Dates Online

Unix Timestamp Converter converts Unix epoch timestamps (10-digit seconds or 13-digit milliseconds) to UTC and local date/time strings, and also converts date strings back to Unix timestamps. Auto-detects whether the input is a timestamp or a date string.

What Is a Unix Timestamp?

A Unix timestamp (also called a POSIX timestamp or epoch time) is the number of seconds that have elapsed since 00:00:00 UTC on Thursday, 1 January 1970 — the Unix epoch. It is the most portable way to represent an absolute point in time because it is timezone-independent: the same integer value means the same instant everywhere on Earth, regardless of local timezone or daylight-saving rules.

Unix timestamps are used pervasively in software: database columns storing creation or modification times, JWT "exp" and "iat" claims, HTTP response headers (Last-Modified, Expires), log timestamps, AWS event times, and API rate limit reset times. The value 0 represents 1970-01-01T00:00:00Z; 1700000000 represents 2023-11-14T22:13:20Z.

A 10-digit Unix timestamp counts whole seconds. A 13-digit timestamp counts milliseconds (multiply by 1000). JavaScript's Date.now() returns milliseconds; Python's time.time() and most Unix system calls return seconds. SmartDevBox auto-detects the scale from the number of digits.

Timezone Gotchas

Unix timestamps are absolute — they represent a single moment in time. The ambiguity only arises when converting to a human-readable date, because that conversion depends on which timezone you apply. "1700000000 in UTC" is 2023-11-14 22:13:20. "1700000000 in US Eastern Time" is 2023-11-14 17:13:20 (UTC−5). SmartDevBox displays both UTC and your browser's local timezone so you can see both representations.

A common mistake is storing dates as local time strings instead of Unix timestamps. If a user in Berlin books an event "for 10:00 AM on 2024-03-31", and you store the string "2024-03-31T10:00:00", a server in New York will interpret that as 10:00 AM EST — two events on the same day at different times. The correct approach: convert to a Unix timestamp at the moment of input (using the user's timezone offset), store the integer, and convert back to local time for display in any timezone.

Common Use Cases

Reading Unix timestamps from server logs or API responses
Converting a specific date/time to a Unix timestamp for queries
Checking when a token or session expires from its timestamp claim

Frequently Asked Questions

How do I convert a Unix timestamp to a readable date?

Paste a Unix timestamp (e.g. 1700000000) into SmartDevBox. The Unix Timestamp tool detects it and shows the equivalent date and time in UTC and your local timezone.

What is the difference between a 10-digit and 13-digit Unix timestamp?

A 10-digit Unix timestamp counts whole seconds since January 1, 1970 UTC. A 13-digit timestamp counts milliseconds. SmartDevBox automatically distinguishes between the two.

Privacy & Security

This tool runs entirely in your browser using client-side JavaScript. No data is sent to a server — your input never leaves your machine. SmartDevBox has no account system, no usage tracking, and no paid tier. See the Privacy & Security page for full details.

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