The clock counts down to midnight at the start of 25 December in your own time zone. Open one advent door a day from 1 December.
Each door unlocks on its date in December. Doors you have opened stay open on this device.
Everything is calculated on your device: no account, nothing stored on a server. On 25 December the page celebrates the day, and from 26 December it switches to next year's Christmas automatically.
The target is the very first moment of 25 December — midnight as it starts — on your own device's clock. The big number counts calendar days, so on 24 December it says one day whether you look at breakfast or just before bed, while the live hours, minutes and seconds below show exactly how long is left.
“Sleeps to go” is the same idea told the way children often ask it: how many nights are left before Christmas morning. Because each place counts down to its own midnight, a friend in another country sees the number that is right for them. Christmas arrives first on Kiritimati in Kiribati (UTC+14) and last in places such as American Samoa (UTC−11), about a day apart.
Dates and habits vary more than you might expect. In Spain and much of Latin America the big family dinner is on Christmas Eve, Nochebuena, and in Spain the season runs on to the Three Kings on 6 January. Mexico celebrates the Posadas on the nine nights from 16 to 24 December. In many parts of Europe Saint Nicholas brings small gifts on 6 December, Sweden marks Saint Lucy's Day on 13 December, and in the UK 26 December is Boxing Day.
In South Korea Christmas has been a public holiday since 1949. Many people spend it with friends or a partner, going out to see the lights, and families with children often keep the gift-giving morning as well.
Advent calendars count the days of December one door at a time. The doors here unlock only on their own date, so there is no opening ahead, and each holds a short activity or a fact about how Christmas is marked somewhere in the world. Door 25 is for Christmas Day itself.
It works well as a small daily routine: open the door at breakfast, or at the start of a lesson, and do the activity together. Opened doors are remembered on the device you used, so you can come back each day and pick up where you left off.
A countdown is most useful when you plan backwards from it. Mark the last posting dates for gifts, the final school or work day, and any trips, then count how many weekends are left between now and the 25th — that is usually the number that decides how much you can fit in.
For any other date — a trip, an exam or New Year's Eve at a set time — use the Day Counter, which counts to any date and time and gives you a link to share.