Countdown Timer

Counting down to a moment

Give the event a name, pick the date and the time, and the countdown shows the days, hours, minutes and seconds left, updating live. Once the moment passes it keeps going the other way, counting the time since, so a countdown to a wedding turns into how long you have been married without you changing anything.

The address bar always holds the countdown on screen. Copy it and send it, and whoever opens it lands straight on the large, full-screen view: the name and four big numbers, nothing to edit in the way. That is the view to put on a television, a projector, or a phone propped on a shelf. While it is full screen the page asks the browser to keep the screen awake, so the display does not go dark half-way through a launch. Press the Exit button, or Escape, to get back to the editor.

Your time, or one time everywhere

Some moments happen at the same wall-clock time wherever you are. New Year is midnight in Tokyo and, hours later, midnight in London; a birthday breakfast is at eight o'clock in whatever town the person is in. Leave In a specific time zone off for those, and each viewer counts down to that time on their own clock.

Other moments are a single instant: a product launch, a live stream, a flight departure, the moment a ticket sale opens. Turn the option on and pick the zone the time is given in. Everyone who opens the link then counts down to the same instant, and the view also shows when that is on the viewer's own clock — useful when the launch is at 9:30 in New York and you are in Berlin. Daylight saving changes are handled for the zone you pick, including a countdown that spans one.

Saving several countdowns

Save keeps the countdown in a list in this browser, so a trip, a deadline and an anniversary can each be one tap away. Opening a saved countdown and changing it offers Save changes; New starts a fresh one without touching the list. The list is stored in your browser's local storage and never leaves the device — there is no account and nothing is uploaded. Clearing the site's data in your browser clears the list, so share a link to anything you would hate to lose.

How the numbers are worked out

The date, time and zone are turned into one exact instant, and the countdown is the difference between that instant and your device's clock, split into whole days of 24 hours, then hours, minutes and seconds. Seconds are rounded toward the moment, so the display reaches zero exactly when it arrives rather than a second early. If your device's clock is wrong, the countdown is wrong by the same amount; phones and computers that set their clocks automatically are accurate to well under a second.

A "day" here is always 24 hours. On the day the clocks change, a countdown to midnight in your own zone gains or loses an hour against a calendar count, which is the real amount of time left. For a count of calendar days between two dates, the date difference calculator is the better tool.