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Unix timestamp converter: seconds, milliseconds and UTC
Choose seconds or milliseconds explicitly before converting. In the reverse direction, enter an ISO date-time with Z or a numeric time-zone offset. The result includes UTC and your browser’s local display, which may differ.
Free to use, with no sign-in. Inputs and results stay in this page and are not sent with the form. Download a result before leaving; this tool does not save your work.
Worked result
1704067200 seconds = 2024-01-01T00:00:00.000Z.
- Multiply seconds by 1000 to obtain milliseconds.
- Interpret the resulting instant on the UTC timeline.
- Format the same instant in UTC and the browser’s local zone.
Convert the start of 2024 in UTC
The timestamp uses seconds since the Unix epoch. JavaScript Date uses milliseconds for the same instant.
Unix seconds: 1704067200
Unix milliseconds: 1704067200000
UTC: 2024-01-01T00:00:00.000Z
2024-01-01T02:00:00+02:00 is the same instant.A local calendar date may differ from the UTC date near midnight. A timestamp identifies an instant; it does not contain a time-zone preference.
A unit and a zone are separate choices
Unix timestamps count elapsed seconds from 1970-01-01T00:00:00Z under the conventional treatment that ignores leap seconds. JavaScript represents the corresponding instant in milliseconds.
An explicit ISO zone makes the reverse conversion unambiguous. A date-time without a zone can be interpreted differently by systems, so this tool rejects it. It also validates calendar components instead of silently accepting an impossible date rolled into the next month.
milliseconds = seconds × 1000
seconds = milliseconds / 1000
ISO UTC example: 2024-01-01T00:00:00Z
Explicit offset example: 2024-01-01T02:00:00+02:00Input limits and common mistakes
Numeric input must resolve to a whole number of milliseconds within the JavaScript Date range. Fractional seconds to millisecond precision are supported; finer precision is rejected. Negative timestamps represent instants before the epoch.
ISO input uses a four-digit year, valid calendar date, T separator, hours and minutes, optional seconds and up to three fractional digits, and Z or ±HH:MM. Leap seconds are not supported. This tool does not compute business days, elapsed calendar months or daylight-saving schedules.
Questions about unix timestamp converter
How do I recognize seconds versus milliseconds?
Common contemporary timestamps often have different digit lengths, but that is not a reliable universal rule. Select the unit from the data source’s documentation.
Can I enter a date-time without a time zone?
No. Include Z for UTC or an explicit offset such as +02:00 to define one instant.
Why can local time show yesterday?
The local offset may place the same instant on a different calendar date from UTC. The underlying timestamp is unchanged.
Sources and verification
These references explain the formulas or formats. The worked examples above were created for this tool and checked against independent calculations or format round trips. AI-assisted development does not imply a named human expert review.
- MDN: Date and timestamps — Epoch milliseconds, UTC/local representations, range and leap-second behavior.
Published 2026-10-23. Examples are illustrations, not measurements of a service or claims about search rankings.
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