Converter
Unix Timestamp Converter
Convert Unix epoch seconds or milliseconds to UTC, local time, and ISO 8601, or turn an ISO date into a timestamp — entirely in your browser.
Timestamps are whole Unix seconds or milliseconds. Dates use ISO 8601; times without a UTC offset are read in your local time zone.
How to convert Unix timestamps
Unix seconds to date
Enter a whole number with an optional leading minus sign to see Unix seconds, Unix milliseconds, UTC ISO 8601, local ISO 8601 with offset, and a readable local line for one instant. 1700000000 Unix seconds × 1000 = 1700000000000 milliseconds, and the UTC result is 2023-11-14T22:13:20Z.
Unix milliseconds to date
1700000000000 is detected as milliseconds and maps to the same 2023-11-14T22:13:20Z instant. The status names the assumed unit and the result echoes both units.
ISO 8601 date to Unix timestamp
Select Date to timestamp and enter an accepted ISO form. 2023-11-14T22:13:20Z returns Unix seconds 1700000000 and Unix milliseconds 1700000000000.
Unix time, UTC, and local time
What is Unix time?
Unix time, or epoch time here, is nominal seconds since 1970-01-01T00:00:00Z, the Unix epoch. POSIX treats every day as 86,400 seconds and does not count leap seconds. Negative timestamps represent instants before the epoch.
How UTC, local time, and offsets work
UTC and local lines are the same instant. The ISO 8601 (UTC) line ends in Z. ISO 8601 (local) uses the browser time zone and numeric ±HH:MM offset, while Local presents that same browser-zone instant in readable form. Date-only means UTC midnight, and a date-time without an offset uses browser local time. In input, Z means UTC, and an explicit ±HH:MM offset is honoured.
Accepted inputs and automatic unit detection
How seconds and milliseconds are detected
Math.abs(value) >= 100,000,000,000 is milliseconds; a lower absolute value is seconds. Positive millisecond values before 1973-03-03T09:46:40Zfall below the threshold and are interpreted as seconds. Negative millisecond values close to the epoch do too. The status discloses the assumption and both unit lines remain visible.
Accepted timestamp and date formats
Timestamp mode trims surrounding whitespace, then accepts whole integers with an optional leading minus sign matching -?\d+. Decimals, commas, leading +, exponents, and internal whitespace are rejected. Date mode accepts YYYY-MM-DD, optionally followed by T or a space plus HH:MM, optional :SS, optional 1–3 fractional-second digits only after seconds, and optional Z or ±HH:MM when a time is present. Natural-language and locale-specific dates are rejected.
Invalid dates and range limits
2023-02-30 is rejected rather than rolled into March. Invalid offsets, shapes, and unparseable dates are rejected. Timestamp numbers must be safe integers and dates stay within JavaScript's ±8,640,000,000,000,000 millisecond range.
Current time and privacy
Use current time takes one snapshot
On click, the browser clock is floored to whole seconds. Timestamp-to-date fills current Unix seconds; date-to-timestamp fills a UTC ISO value ending in Z; the current mode converts it immediately. It is one click-time snapshot, not a live clock, countdown, server-synchronized time, auto-refresh, or relative-time display.
Private, browser-based conversion
Your timestamp or date is processed in this browser. It is not uploaded or sent to a 247 Tools server, and the converter does not save a conversion history. Clear removes the current input and result from the page.