How the sleeps are counted
The countdown looks at your device's clock, finds the next 25 December, and counts two things at once. The sleeps figure is the number of nights between now and Christmas morning: on Christmas Eve it says 1, and on the day itself it says 0. The days, hours, minutes and seconds underneath measure the exact time remaining until midnight at the very start of Christmas Day, refreshing every second.
The two figures can look slightly different, and both are right. At 9pm on 23 December you still have 2 sleeps ahead of you, but the clock shows 1 day and 3 hours, because a "day" on a countdown is a full 24 hours rather than a square on the calendar. Children count sleeps; project managers count hours. This page keeps both camps happy.
Worked examples
Why sleeps, not days
Ask a five year old how long until Christmas and "17 days" means very little, but "17 more sleeps" is something they can genuinely picture: that many bedtimes, that many mornings. The habit almost certainly stuck because it maps onto the advent calendar, which turns the last 24 sleeps into a door a day. It is also more honest than it sounds. Christmas does not arrive at some abstract midnight moment for most households; it arrives when you wake up. Counting the nights you still have to get through is exactly the right measure of the wait.
Sleeps also sidestep an ambiguity that trips up ordinary day counting. Does "3 days until Friday" include today? Does it include Friday? Nights have no such problem: you either sleep through one more of them or you do not, so everyone lands on the same number.
It rolls over by itself
There is nothing to set and nothing to update. The countdown always targets the next 25 December: through spring and summer it counts towards this year's Christmas, on the day itself it stops to wish you a merry one, and from Boxing Day it quietly starts again on the following year. Bookmark the page on Boxing Day 2026 and it will already be counting the 364 sleeps to the next one without being asked.
A little seasonal trivia for the wait. Christmas Day 2026 falls on a Friday, which is why the substitute bank holiday for Boxing Day (a Saturday that year) lands on Monday 28 December. The weekday moves forward one place each year, and two after a leap year's 29 February slips in, so Christmas 2027 falls on a Saturday. And because the countdown runs entirely in your browser from your own clock, midnight means your midnight: children in Auckland start unwrapping about 13 hours before children in London, and both countdowns are correct. If you want to count down to something other than Christmas, the countdown to a date tool does the same job for any date you choose.
Frequently asked questions
What exactly is a sleep?
A sleep is one night between now and Christmas morning. On Christmas Eve there is 1 sleep left, and on Christmas Day itself there are none. It is the way most families count with children, because nights are easier to picture than 24-hour blocks.
Why do the sleeps and the days figures sometimes differ?
Sleeps count whole nights, while the days figure measures exact elapsed time to midnight at the start of 25 December. At 9pm on 23 December there are 2 sleeps left but only 1 full day and 3 hours on the clock. Both are correct; they answer slightly different questions.
Does it work after Christmas has passed?
Yes. Once Christmas Day is over, the countdown rolls over automatically and starts counting towards 25 December of the following year. You never need to change a setting, whatever the date.
Which time zone does the countdown use?
Your device's own clock. Christmas arrives at midnight local time wherever you are, so the countdown always matches what your calendar says. Nothing is stored or uploaded; everything runs in your browser.
How many sleeps until Christmas from 1 December?
24 sleeps, which is exactly why advent calendars have 24 doors. Each door you open is one sleep crossed off, with the last opened on Christmas Eve.