Unix Timestamp Converter — Epoch to Date

const millis = Date.now();
const seconds = Math.floor(millis / 1000);
console.log(seconds, millis);

What it is

A Unix timestamp (epoch time) counts the time since 1970-01-01 00:00:00 UTC as a single number. You meet it in logs, databases, API responses and the exp claim of a JWT, but you cannot read it at a glance. This tool turns an epoch into a readable date and a date into an epoch. The top card shows the current Unix time in seconds and milliseconds, live, and the card beside it sets the time zone for every conversion. Below are period start and end, a seconds-to-duration converter, a time-to-seconds table and code samples.

How to use

1. Epoch to date: paste a timestamp. Seconds, milliseconds, microseconds and nanoseconds are detected automatically, and you get the local date, UTC, ISO 8601, RFC 2822, HTTP date, relative time, weekday, ISO week and day of the year.
2. Date to epoch: under “Type in fields” enter year, month, day, hour, minute and second (milliseconds optional) in separate boxes. The up and down arrow keys change a value, pasting a whole date into any box fills them all, and “Now” inserts the current time. A 24-hour or AM/PM style and a UTC toggle are there too.
3. Prefer a picker? Choose “Calendar and clock picker”. Prefer writing the date as text? Choose “Free-text date”; it is parsed as you type.
4. Start and end of a year, month or day: pick the period and the date to get the first moment and the last second as timestamps.
5. Seconds to duration: enter a number of seconds to see it as years, months, days, hours, minutes and seconds. Use the copy button beside any result.

How it works

• Unit rule on the absolute value: under 1e11 seconds, under 1e14 milliseconds, under 1e17 microseconds, otherwise nanoseconds. Negative values are before 1970.
• ISO 8601 is shown in UTC (Z) and with the offset of the selected zone (+09:00). For microsecond and nanosecond input the UTC value is written out to nine fractional digits.
• RFC 2822 is the email-header format with an offset; the HTTP date is the GMT format of the Date and Expires headers (RFC 9110). Week numbers follow ISO 8601: weeks start on Monday and week 1 holds the first Thursday.
• Start and end: the start is 00:00:00 in the zone, and the end is the next period start minus one second. A day with a daylight-saving change is 23 or 25 hours long, and where midnight itself is skipped the first time that actually exists is used.
• The duration breakdown uses averages: a year is 365.25 days (31,557,600 s) and a month is one twelfth of that (2,629,800 s).
• A wall-clock time that a daylight-saving jump skips is an error, and a time that occurs twice resolves to the earlier one.

Examples

Input	Read as	UTC date
0	seconds	1970-01-01T00:00:00.000Z
1700000000	seconds	2023-11-14T22:13:20.000Z
1700000000123	milliseconds	2023-11-14T22:13:20.123Z
1700000000123456	microseconds	2023-11-14T22:13:20.123456000Z
1700000000123456789	nanoseconds	2023-11-14T22:13:20.123456789Z

The same 1700000000 in Korea is 2023-11-15 07:13:20 (+09:00), and Oct 4, 2026 3:05 PM in Seoul is 1791093900.

Notes

• When timestamps in two logs look out of step, check the unit and the zone first. One side being seconds and the other milliseconds is very common.
• JavaScript Date.now() returns milliseconds, while most Unix tools and UNIX_TIMESTAMP() in databases return seconds. The code samples at the bottom show the call for each language.
• In a zone with daylight saving, such as America/New_York, a time skipped in spring is reported as nonexistent.