What the result contains
What This Tool Provides
Convert Unix epoch values to one instant shown as ISO 8601, UTC, and browser-local time, or convert a local date/time back to seconds and milliseconds. Auto mode recognizes conventional 10-digit seconds and 13-digit milliseconds, with explicit unit controls for ambiguous values.
- Unix seconds and milliseconds
- ISO 8601 and UTC output
- Your browser’s local date/time display
- Auto, seconds, and milliseconds input modes
How to Use This Tool
- Enter a valuePaste a numeric epoch value or choose a local date and time.
- Confirm the unitUse Auto for typical 10/13-digit values or select seconds/milliseconds explicitly.
- Compare displaysRead the same instant in UTC, ISO, and your browser’s local timezone.
How It Works
Unix time measures elapsed seconds from 1970-01-01 00:00:00 UTC. JavaScript Date stores milliseconds, so seconds are multiplied by 1,000 and milliseconds are used directly. datetime-local input is interpreted in the browser’s local timezone; timezone formatting changes the clock display, not the instant.
Worked Examples
Unix epoch
- Input
0 seconds- Output
1970-01-01T00:00:00.000Z
Zero is the UTC epoch reference instant.
Seconds and milliseconds
- Input
1704067200 / 1704067200000- Output
2024-01-01T00:00:00.000Z
The 10-digit seconds and 13-digit milliseconds forms represent the same instant.
Where Epoch Values Come From
Almost every epoch value you paste here came out of a JSON payload, where created_at, iat, and exp sit as bare numbers — formatting that payload makes them findable in the first place. Inside a JWT they are only visible after decoding the Base64 segment.
Once converted, the question is usually about a gap: the interval between two dates or the days until an expiry, or an age from a stored birthdate.
Seconds, Milliseconds, and Timezones
| Value shape | Typical unit | Advice |
|---|---|---|
| 10 digits | Seconds | Auto mode normally treats it as seconds |
| 13 digits | Milliseconds | Auto mode normally treats it as milliseconds |
| Short or historical value | Ambiguous | Choose the unit explicitly |
| datetime-local | Browser local time | Compare UTC output after conversion |
Where Epoch Values Appear
- API response fields
- Database created/updated columns
- Log records
- Token expiration values
- Scheduled events and queues
Important Edge Cases
- Negative values represent instants before 1970 when supported by JavaScript Date.
- A short millisecond value can look like seconds, so explicit units matter.
- Daylight-saving rules affect local display but not the underlying epoch value.
Limitations
- The page shows UTC and the browser’s local timezone; it has no arbitrary IANA timezone picker.
- It does not parse dates embedded in prose.
- The supported range is the JavaScript Date range, not every date a database may store.
Input handling
Private Browser Processing
Timestamp and date values are converted locally and are not submitted to Tiny Tiny Tools.
Google Analytics records page visits and whether a tool finished or failed, but these tool implementations do not send field values, generated passwords, QR payloads, uploaded QR images, or camera frames to analytics or a Tiny Tiny Tools processing endpoint.
See the Privacy Policy for site-wide details.
Questions About This Tool
What is the Unix epoch?
It is 1970-01-01 00:00:00 UTC, the zero reference for Unix timestamps.
How does auto-detection work?
Values with an absolute magnitude of at least one trillion are treated as milliseconds; smaller values are treated as seconds. Select a unit for ambiguous historical values.
Does a Unix timestamp contain a timezone?
No. It represents an instant. UTC or local formatting determines the displayed clock time.
Are dates before 1970 supported?
Yes, negative seconds can be converted when they remain inside the JavaScript Date range.