Unix time zero
0 seconds is 1970-01-01 00:00:00 UTC and 1970-01-01 09:00:00 KST.
Unix timestamp · date conversion
Convert a Unix
timestamp to a date
Convert 10-digit seconds, 13-digit milliseconds, microseconds or nanoseconds into readable dates. Compare the same instant in UTC, Korea Standard Time, your device time zone and a selected city.
Estimating the unit from digit count
Digit length is a useful clue near present-day dates, but the documented source unit always takes priority for historical or far-future values.
| Digit guide | Likely unit | Example | What to verify |
|---|---|---|---|
| 1–10 digits | Seconds | 1704067200 | Present-day seconds are usually 10 digits |
| 11–13 digits | Milliseconds | 1704067200000 | Usually 1,000 times the seconds value |
| 14–16 digits | Microseconds | 1704067200000000 | 1,000 times finer than milliseconds |
| 17+ digits | Nanoseconds | 1704067200000000000 | Keep the value as an integer string |
Precision is preserved. Large inputs are converted as integer nanoseconds without intermediate rounding. Fractional precision is retained in the ISO result where the date range permits.
Known values for checking a result
Use boundary values to confirm both the selected unit and the converter output.
First instant of 2000
946684800 seconds is 2000-01-01 00:00:00 UTC, a convenient test value.
32-bit boundary
2147483647 seconds is 2038-01-19 03:14:07 UTC. The next second exceeds signed 32-bit storage.
One instant, many local clocks
A timestamp identifies one instant regardless of region. Choosing a time zone changes the calendar and clock used to display that instant, not the underlying Unix value.
UTC
The global reference used to compare records from different regions.
Korea Standard Time
KST is UTC+09:00 all year and currently has no daylight-saving changes.
Named city zones
New York, London and Sydney follow date-specific regional rules, including seasonal changes.
Display range: extremely large values cannot be represented as ordinary calendar dates. If you see a range error, check whether seconds were interpreted as milliseconds or vice versa.
Regional rules follow the IANA Time Zone Database. The calendar display limit is described in MDN's Date documentation.
Timestamp-to-date questions
Four checks to make when a converted date is not what you expected.
Why does my timestamp convert to a date in 1970?
The most common cause is a seconds-versus-milliseconds mismatch. Check whether a 13-digit millisecond value was read as seconds or a 10-digit seconds value was read as milliseconds.
Can I convert fractional Unix time?
Yes. Seconds can contain up to nine fractional digits, milliseconds up to six and microseconds up to three. Nanoseconds must be entered as an integer.
What does a negative timestamp mean?
A negative value represents an instant before 1970-01-01 00:00:00 UTC. For example, -1 second is 1969-12-31 23:59:59 UTC.
Why can the UTC and Korea dates be different days?
Korea Standard Time is nine hours ahead of UTC. A late-afternoon UTC instant can already be the next calendar day in Korea.
Continue with another conversion
Create a timestamp from a date, process many values or validate a date string.
Reverse direction
Date → Unix time
Calculate seconds and milliseconds from a calendar date.
Convert a date →Many valuesBatch date conversion
Turn multiple numbers into a UTC and KST table.
Convert a batch →String validationISO 8601 validator
Check the syntax and time-zone offset of a date string.
Validate a format →