semkuUnix timestamp converter
Convert timestamps to dates, or dates to timestamps.
Date formats and units
Date to timestamp
Conversion rules
Unix time counts seconds from midnight UTC on January 1, 1970, without counting leap seconds.
Auto reads absolute values below 100000000000 as seconds and values from 100000000000 to below 100000000000000 as milliseconds. Larger values require a unit choice, subject to input and date limits. Choose Seconds or Milliseconds to override Auto.
Dates use the proleptic Gregorian calendar, extending its rules to earlier years, with UTC years from 0001 to 9999. Negative timestamps are allowed. Inputs accept integers only; values with 16 or more digits are rejected before unit detection.
Local uses this device’s time zone. Time zone rules come from the browser, so local and selected-zone results can differ between browsers. Historical offsets may include seconds.
During a daylight saving change, a repeated time returns both matching timestamps with their offsets. A time that does not exist is rejected without moving it to another time.
Convert seconds and milliseconds using UTC, this device’s local time zone, or one additional selected time zone.
Unix time = seconds since midnight UTC on January 1, 1970. Each day counts as 86400 seconds, without leap seconds. Milliseconds = seconds × 1000. Auto uses seconds for |n| < 100000000000 and milliseconds for 100000000000 ≤ |n| < 100000000000000; otherwise choose a unit within the supported input range.
Frequently asked questions
- How are seconds and milliseconds detected?
- Auto uses the absolute value: below 100000000000 means seconds, and from 100000000000 to below 100000000000000 means milliseconds. Larger values need a unit choice if they pass the input limit. The result states the unit used. Choose Seconds or Milliseconds if your intended unit differs.
- Why does someone else see a different local time?
- Local uses each device’s time zone, so the same timestamp can show a different local date or time. The UTC result represents the same instant. Check the displayed time zone name and offset when comparing results.
- Why can a local time occur twice or not exist?
- A daylight saving clock change can repeat or skip a time. This converter shows both matching timestamps for a repeated time and rejects a skipped time without shifting it. This applies to the device’s local zone and the additional selected zone.
- Can I convert a negative timestamp?
- Yes. A negative timestamp represents an instant before midnight UTC on January 1, 1970. Use a leading minus sign and choose the intended unit. The resulting UTC year must be from 0001 to 9999.
- What is the year 2038 problem?
- A signed 32-bit integer holds at most 2147483647 seconds, corresponding to January 19, 2038 (Tue) at 03:14:07 UTC. Systems that store Unix seconds that way may be affected beyond that point. This converter supports UTC years through 9999, but its result does not establish another system’s limits.
Privacy on this page
Conversions run in your browser. semku does not send your timestamps, dates, times, time basis, results or copied text to the server or keep them in browser storage. Input state after the # in the URL is shared when you share that URL, but is not included in the page request sent to the server. This state includes the timestamp, unit, date, time and UTC or Local basis. Time zone names are not included, so an additional selected time zone must be chosen again. Local reads this device’s time zone setting without sending or saving the setting. The current timestamp uses this device’s clock.
To understand how the page is used and to improve the service, this page sends semku’s own usage statistics and automatic error reports. They go only to the dedicated endpoint under semku.com/api/telemetry/v1/. They are not used for advertising or third-party tracking.
The usage statistics include stages of use (such as starting an operation or requesting a copy), the times they occur and fixed identifiers that distinguish the page and feature. They do not include timestamps, dates, times, the time basis, time zone names, conversion results or copied text. Inputs are not sent as hashes or as size categories either. The full URL and search terms are not sent.
Operations and sessions are distinguished by randomly generated identifiers. In the browser, these identifiers exist only in temporary memory and are not written to cookies or browser storage. No identification based on cookies or combined device characteristics is used.
Error reports contain the error type, code and time, and, where available, a registered program-source identifier with line and column numbers. The error message text and stack traces are not sent. Usage statistics and error reports also carry the site identifier, the deployment version and a random record identifier. For access records such as IP addresses, browser signals (User-Agent Client Hints), region and language, see the paragraph below.
The feedback form sends the rating you chose and the text you typed in the free-text field when you press the send button. The form also sends a random ID that distinguishes the submission, along with the page, site, deployment version and type of request. There are no fields for your name, email address or phone number, and timestamps, dates, times, the time basis, time zone names, conversion results or copied text are not attached automatically. Before sending your text, the widget removes leading and trailing whitespace and, if you selected a rating, adds [+1] or [-1] at the start; it makes no other changes to your text. After receipt, the collector standardizes line endings and removes leading and trailing whitespace. Please do not enter personal data, passwords, authentication keys or payment details.
To improve the service, we record the country and state/province-level region at the time of your visit (an estimate based on the connecting network), which site you came from including the page path, and one display-language setting announced by your browser (for example, en-US). Location is kept to country and region only; no city or precise position is recorded. When you use the service, connection records, including your IP address, are automatically generated and retained to maintain service security and identify abnormal access. Cloudflare is the data processor for this site. Collection of this item is enabled only after this notice is published; we do not collect it retrospectively for use before collection is enabled. Query strings such as search terms are not recorded, and neither is the full list of preferred languages or the raw request headers. Collection of this information is currently disabled and will only be enabled after this notice is published. If we enable collection, we will collect and use signals your browser reports about its type and version, along with an indication of whether automation tools are being used, to identify bots. These browser signals are estimates and do not conclusively identify your browser's type or version or whether automation tools are being used. We do not collect it retrospectively for use before collection is enabled. The raw User-Agent request header is not recorded. These records are per visit only and use no identifier that links one visit to another. Recording starts only with visits after this notice is published and is not applied retroactively to earlier visits. The region and the referring site have been recorded since 2026-09-20; the display language since 2026-09-24. Browser signals are not recorded yet.
Separately, when you visit the site, the hosting provider records your IP address, the time of the request and user-agent information about your browser and device in Cloudflare Pages’ standard access logs.
For details, see the privacy policy.
Calculations run in your browser without sending your calculation inputs or results to the server.