# What day is it today?

Today's date depends on where you are: the live answer for UTC is at https://whathappen.today/api/today, and ?tz=Area/City gives it for any time zone.

Today's date where you are, from your device's clock and time zone — with the week number, how far through the year we are, the moon, and who has a public holiday.

## The short answer

The first line of this page is today's date: on our server it is the UTC date, the same sentence the [date API](https://whathappen.today/api/) returns, and once the page loads it switches to your own time zone. Each calendar date is in use somewhere on Earth for about 50 hours, because clocks run from UTC−12 to UTC+14. ISO weeks run Monday to Sunday; 2026 has 53 ISO weeks and 365 days, and the next leap year is 2028.

## How the date is worked out

A date is not a single global fact. At any moment the world spans two calendar days, and for two hours each day it spans three: at 11:30 UTC, for example, it is already tomorrow on Kiritimati in the central Pacific (UTC+14) and still yesterday on Baker Island (UTC−12). So this page starts from the one thing that is the same everywhere — the current instant — and converts it into a date using your device's time-zone setting, including any daylight-saving offset in force today.

Everything is calculated in your browser with the time-zone database built into it. The page does not ask for your location, does not use cookies, and does not send your time zone to us. The UTC line under the date is there as a reference: it is the date most servers, logs and many AI models use by default.

## Week numbers

Two week-numbering systems are in common use and they disagree for part of the year. The **ISO 8601** week starts on Monday, and week 1 is the week that contains the first Thursday of January — equivalently, the week with 4 January in it. A year therefore has 52 or 53 ISO weeks, and the first days of January can still belong to the last week of the previous year. The **US convention** starts weeks on Sunday and simply calls the week containing 1 January week 1. Planners, payroll systems and spreadsheets usually say which they mean; if not, European ones nearly always mean ISO. The [week number page](https://whathappen.today/week-number/) lists every week of the year with its dates.

## Day of the year

The day of the year counts 1 January as day 1, so 31 December is day 365, or 366 in a leap year. Leap years are those divisible by 4, except century years that are not divisible by 400: 2000 and 2024 were leap years, 2100 will not be. The percentage shown is how much of the year has passed at the start of today. There is a full table on the [day of the year page](https://whathappen.today/day-of-the-year/).

## Public holidays today

The holiday list checks each of the 20 countries we cover against *its own* date, not yours: a holiday in New Zealand begins while it is still the previous evening in Europe. Substitute days off — when a holiday falls on a weekend and the day off moves — are marked, and so are holidays whose date depends on sighting the new moon. For China, weekend days that become working days under the official holiday arrangement are shown too. Each country page links to its government's own list, which is the one to trust when they disagree.

## For programs and AI assistants

Language models often do not know today's date, and when they do it is usually the UTC date rather than the user's. The same facts on this page are available as JSON:

```
curl "https://whathappen.today/api/today?tz=Asia/Tokyo&country=JP"
```

The answer includes the local date, weekday, ISO week, day of the year, the moon phase, whether it is a public holiday, the next holiday, and a one-sentence summary an assistant can quote. An MCP endpoint at `/mcp` offers the same as tools. See the [API and MCP documentation](https://whathappen.today/api/).

## Worked example: one moment, four places, three dates

At 11:30 UTC on 9 October 2026 the same instant falls on three different calendar days:

| Place | Local date and time |
| --- | --- |
| Kiritimati, Kiribati | Saturday 10 October 2026, 01:30 |
| London | Friday 9 October 2026, 12:30 |
| New York | Friday 9 October 2026, 07:30 |
| Baker Island (UTC−12) | Thursday 8 October 2026, 23:30 |

That is why the date API asks for a time zone: without one it answers for UTC, which can be a day off for anyone far east or west of Greenwich.

## Limits

- The page uses your device's clock and time-zone setting; if either is wrong, so is the date shown.
- Holiday lists cover 20 countries, 2020–2030, national holidays only; they are for reference.
- Moon phase moments are calculated to within about 20 minutes, so a phase that happens close to midnight can be named on the neighbouring day.

## Sources

- [ISO — ISO 8601 date and time format](https://www.iso.org/iso-8601-date-and-time-format.html) — week numbering and YYYY-MM-DD dates (checked 2026-10-10)
- [IANA — Time Zone Database](https://www.iana.org/time-zones) — time-zone offsets and daylight-saving rules (checked 2026-10-10)
- [U.S. Naval Observatory — Moon phases data](https://aa.usno.navy.mil/data/MoonPhases) — reference times we test our moon phases against (checked 2026-10-10)
- [vacanza/holidays (open-source holiday rules, MIT licence)](https://github.com/vacanza/holidays) — holiday rules used to build the lists (checked 2026-10-10)

## Questions and answers

How do you know what day it is for me?

Your browser reports its clock and its time zone setting (for example `Europe/Berlin`). The page turns the current instant into a calendar date in that zone, so nothing is looked up on a server and nothing about you is sent anywhere. If your device clock is wrong, the date shown here will be wrong too.

Why is the UTC date different from mine?

UTC is the reference clock the world's time zones are measured from. Between your local midnight and midnight in UTC the two dates differ: in Sydney or Tokyo you are a day ahead of UTC in the morning, and in New York or Los Angeles you are a day behind it in the evening.

Which week number is correct, ISO or US?

Both, under different rules. ISO 8601, used across Europe and in most software, starts weeks on Monday and counts the week containing the year's first Thursday as week 1. The common US convention starts on Sunday and counts the week containing 1 January as week 1. Near New Year they can be a week apart, and late December can even belong to ISO week 1 of the next year.

Does the page update at midnight?

Yes. The page checks the clock every second and redraws everything when your local date changes, so a tab left open overnight shows the new day without a reload.

How is the moon phase worked out?

From the positions of the Sun and Moon at local noon, using standard astronomical formulas. A day is labelled New Moon, First Quarter, Full Moon or Last Quarter when that exact moment falls within your local day, the way printed calendars do; on other days you see the waxing or waning crescent or gibbous phase and the lit fraction of the disc.

Can a program or AI assistant get the same answer?

Yes. `/api/today` returns the same facts as JSON for any time zone and, with a country, the holiday status; the [API page](https://whathappen.today/api/) also explains the MCP endpoint for AI assistants. Both are free and need no key.

Dates and times depend on your device's clock and time-zone setting. Holiday information is for reference only and may change at short notice; confirm with the official source before booking travel or planning work.

Last updated: 10 October 2026

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Web page: https://whathappen.today/