Unix Timestamp Converter
Convert Unix timestamps in seconds or milliseconds to local time, UTC, and ISO 8601. All calculations stay in your browser.
This tool runs entirely in your browser. Your input is never uploaded.
Current time
Browser local time zone
Timestamp to date
Choose the timestamp unit, then view local, UTC, and ISO 8601 time.
Date to timestamp
Choose how to interpret the date, then generate Unix timestamps in seconds and milliseconds.
What is a Unix timestamp?
A Unix timestamp represents elapsed time since 1970-01-01T00:00:00Z, known as the Unix epoch. The timestamp itself has no time zone and describes one absolute moment worldwide.
Seconds and milliseconds
Many backend systems use timestamps in seconds, while JavaScript Date uses milliseconds. They usually differ by a factor of 1000. For example, 1704067200 seconds and 1704067200000 milliseconds both represent 2024-01-01T00:00:00Z.
This tool asks you to choose the unit explicitly instead of guessing from the number of digits, which can be unreliable for early dates and unusually large values.
Local time and UTC
UTC is a global time standard independent of location. Local time comes from the browser device's time zone, such as America/New_York. One timestamp can display different dates or hours in different time zones while still representing the same instant.
ISO 8601
ISO 8601 is a common machine-readable format, such as 2024-01-01T00:00:00.000Z. A trailing Z indicates UTC. APIs, logs, and databases frequently use this format to exchange dates.
Which zone should I use for date input?
Local mode interprets the entered calendar date in the browser's current time zone. UTC mode interprets the same fields as UTC. In regions with daylight saving time, some local times may repeat or not exist because of time zone transitions.
Zero and negative timestamps
Timestamp 0 is valid and represents the Unix epoch. Negative values represent moments before 1970 and can be converted as long as they remain within the JavaScript Date range.
Privacy and security
All date calculations run locally in your browser. Timestamps and dates are not uploaded, added to the URL, or stored locally.
Frequently asked questions
Why is the converted date several hours different?
The most common reason is mixing local time with UTC. Check the intended zone of the input and the browser time zone displayed by the tool.
Why are JavaScript timestamps usually 13 digits?
JavaScript uses milliseconds since the Unix epoch, which commonly produces 13 digits for modern dates. Many server languages use seconds, commonly producing 10 digits. Digit count is only a convention and should not be the sole detection method.
Do leap years affect timestamps?
Timestamps count continuous elapsed seconds or milliseconds. When displaying a calendar date, the browser applies Gregorian calendar rules, including leap years.