Unix Timestamp Converter (KST)
Convert a Unix timestamp (epoch time) to Korea Standard Time (KST) and UTC, or a KST date back to seconds and milliseconds. It tells seconds from milliseconds by digit count and shows the current timestamp live.
How to use
- Type a number in the timestamp field. 10 digits are read as seconds and 13 digits as milliseconds; you can also pick the unit by hand.
- KST, ISO 8601, RFC 2822, UTC and a relative time (days ago or from now) appear at once. Each row has its own copy button.
- To go the other way, enter a Korean local date such as 2009-02-14 08:31:30 in the second field to get seconds and milliseconds.
- The Now button fills in the current timestamp.
FAQ
What is a Unix timestamp?
The number of seconds since 1970-01-01 00:00:00 UTC (the epoch). POSIX counts every day as exactly 86400 seconds, with no leap seconds. For example 1234567890 is 2009-02-13 23:31:30 UTC, which is 2009-02-14 08:31:30 in KST.
How does it tell seconds from milliseconds?
By digit count: about 10 digits is seconds, 13 is milliseconds, 16 is microseconds and 19 is nanoseconds. If a value is ambiguous, choose the unit yourself. JavaScript's Date.now() returns milliseconds.
How far is KST from UTC?
KST is UTC+9 all year, with no daylight saving time. A timestamp has no time zone, so the tool adds nine hours to the UTC result to show KST.
What is the year 2038 problem?
A signed 32-bit integer tops out at 2147483647 (2038-01-19 03:14:07 UTC) and overflows one second later. The lower limit is -2147483648 (1901-12-13 20:45:52 UTC). A value outside that range gets a warning here.
How do I convert it in Excel?
If the value in seconds is in A1, use =A1/86400+25569+9/24 and format the cell as date and time. 25569 is the number of days from 1900-01-01 to 1970-01-01, and 9/24 is the KST offset. Divide by 1000 first for milliseconds.
Are leap seconds counted?
No. POSIX time has no leap seconds, so every day is 86400 seconds. Around a real leap second the timestamp repeats or stalls instead of showing a 61st second.
AI agents: this calculation is available over an API without the form — see /llms.txt and the tool list at /api/calc; confirm the final result on this page.