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Free Online ISO 8601 Date, Time and Duration Converter

Paste any ISO 8601 timestamp and see it as a calendar date, a week date, an ordinal date, in basic and extended form, in UTC and at its own offset. The page also builds a timestamp from parts and converts ISO 8601 durations such as P1DT2H30M into plain hours and minutes, explaining whatever it cannot read.

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Free Online ISO 8601 Date, Time and Duration Converter

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🧩 ISO 8601 Reader and Builder Every form of the same moment · durations too · nothing guessed

Every date is worked out in your browser. Nothing you type is sent anywhere.

🧩 What have you got?

The ISO 8601 string Calendar dates, week dates, ordinal dates, basic or extended form, with Z, with an offset, or with none at all.

Try one of these

Extended form

—

In UTC—

Week date—

Ordinal date—

Basic form—

Unix seconds—

How the string was taken apart.

Part	Value	What it means

The same moment as	Written out	Where this form turns up

Recent conversions, kept in this browser only.

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How to Read an ISO 8601 Timestamp

Three modes, one standard.

Paste the string Any ISO 8601 form: a calendar date, a week date such as 2026-W41-3, an ordinal date such as 2026-276, the basic form without separators, with Z, with an offset or with none.

Read every other form of it The same moment written as extended and basic form, in UTC and at its own offset, as a week date and an ordinal date, with the weekday, the unix timestamp and the ISO week number beside it.

Or go the other way Build a timestamp from a date, a time and an offset, or convert a duration such as P1DT2H30M into plain hours and minutes. Anything that cannot be read is explained rather than refused.

What to Know About ISO 8601

The forms that are valid, and the ones that only look valid.

No offset does not mean UTC. A string such as 2026-10-03T14:30 carries no offset, and the standard reads it as local time, which means it points at a different moment depending on where it is read. Z means UTC exactly. Treating the two as the same is a bug that moves a timestamp by hours and only shows up on a machine in another country.

Week dates and ordinal dates are not exotic. 2026-W41-3 is the Wednesday of the forty first ISO week, and 2026-276 is the two hundred and seventy sixth day of the year. Both are ordinary ISO 8601, both appear in real log files and industrial systems, and most converters simply refuse them. This one reads them and writes them.

The ISO week year is not always the calendar year. 1 January can fall in the last ISO week of the previous year, and 31 December can fall in week one of the next. So 2027-01-01 is 2026-W53-5 in week date form. Mixing the calendar year with the week year is a classic off by one that appears once a year, at the worst possible moment.

A space instead of the T is common and not standard. Databases often print 2026-10-03 14:30:00 with a space, which the standard does not allow in that position. The page reads it anyway and says that it did, because refusing it would help nobody, but it is worth knowing before putting the string somewhere stricter.

Durations are a separate part of the standard. PT8H30M is a length of time, not a moment, and it is why the T matters: P1M is one month and PT1M is one minute. The week form P6W cannot be mixed with the others. Months and years in a duration have no fixed length, so this page converts them at a stated average and says so.

It runs in your browser with nothing uploaded. The parsing is in the page, so it works offline once loaded and nothing you paste is sent anywhere.

Key Features & Capabilities

What it reads, and what it deliberately leaves alone.

Every form read Calendar, week and ordinal dates, basic and extended, with Z, an offset or none.

Every form written The same moment in each of those forms side by side, with the unix timestamp.

Durations as well P1DT2H30M and P6W turned into hours and minutes, with the months caveat stated.

Explains what it cannot read Which part of the string broke the rule, rather than a bare invalid date.

The ISO week year Shown separately from the calendar year, because at the turn of the year they differ.

Nothing is uploaded It runs in this tab and keeps working offline.

About ISO 8601

ISO 8601 is the international standard for writing dates and times, and its whole purpose is to remove ambiguity. 03/10/2026 is the third of October in most of the world and the tenth of March in the United States; 2026-10-03 is the third of October everywhere. The ordering from largest unit to smallest also means that sorting such strings as plain text sorts them chronologically, which is why almost every log file, API and database interchange format in use settled on it.

The standard is wider than the one form most people have met. Besides the calendar date there is the week date, 2026-W41-3, which names the Wednesday of the forty first week, and the ordinal date, 2026-276, which names the day by its position in the year. There is a basic form without separators, 20261003T143000Z, used where every character counts. All of these are correct ISO 8601, all of them appear in real data, and a converter that only handles the familiar form is of no use when one of the others turns up.

The offset is where the real mistakes live. A string ending in Z is in UTC and names an exact moment. A string ending in +05:00 names the same kind of exact moment, read on a clock five hours ahead. A string with no offset at all is local time, which means it does not name a single moment until you know whose local time is meant, and code that treats a missing offset as UTC moves every such timestamp by hours. The page always states which of the three cases it found, because the difference cannot be seen by looking at the string.

Durations are a separate part of the standard and use their own grammar, starting with P. The T inside them is not decoration: P1M is one month and PT1M is one minute, which is a difference of about forty three thousand to one. Weeks have their own form, P6W, which cannot be combined with the other parts. Years and months have no fixed length, so a duration containing them cannot be turned into an exact number of hours; this page converts them at a stated average and labels the result as approximate rather than pretending otherwise.

Frequently Asked Questions

Z, offsets, week dates and durations.

UTC, with no offset. It is read as zulu time, and it names an exact moment. An offset such as +05:00 also names an exact moment; no offset at all means local time and does not.

A week date: the third day, which is Wednesday, of the forty first ISO week of 2026. ISO weeks start on Monday and week one is the week containing the first Thursday of the year.

An ordinal date: the two hundred and seventy sixth day of 2026, which is 3 October. It is sometimes loosely called a Julian day, although that name belongs to a different count.

Because the ISO week year follows the weeks, not the calendar. 1 January can belong to the last week of the previous year, so 2027-01-01 is written 2026-W53-5.

Not strictly: the standard wants a T between the date and the time. Databases print it with a space very often, so this page reads it and tells you it is a deviation.

An ISO 8601 duration of eight hours thirty minutes. The P starts a duration and the T separates the date parts from the time parts, which is why PT1M is a minute and P1M is a month.

No. The parsing runs in your browser, so nothing you paste leaves the page and it works offline.