Countdown to a Date

How long until your date?

Enter a date, a time and the time zone they belong to, and the countdown shows the days, hours, minutes and seconds left, ticking every second. Under it are the same wait in weeks and days, in total days, hours, minutes and seconds, and as months and days on the event’s own calendar. Once the moment passes, it counts the time since instead.

How to use the countdown

• Event name (optional): shown above the countdown and in a shared link.
• Date and Time: the moment as the event’s own clock shows it. Leave the time blank for the start of the day (12:00 AM). Leave the date blank to count down to the next time the clock shows that time, such as 5:00 PM today, or tomorrow once today’s has passed.
• Time zone: where that date and time apply. Type a city, a country or an IANA name such as Europe/London and pick from the list. Leave it blank, or press Use my time zone, for your own.
• Clock: 12-hour or 24-hour times in the results.

The Try buttons work out their dates when you press them, so “Christmas Day” is always the next December 25, never a stale year. New Year in Sydney counts down to midnight there, which arrives hours before midnight in Europe and the Americas.

How the countdown is calculated

The target is a clock reading in a time zone, so it is first turned into an instant in UTC with that zone’s offset on that date:

$$t_{\text{UTC}} = t_{\text{local}} - \text{offset}$$

The time left is the difference between that instant and now, rounded up to whole seconds while the target is ahead, so the display reaches zero exactly on time:

$$s = \lceil t_{\text{target}} - t_{\text{now}} \rceil$$

The seconds $s$ then split into 24-hour days, hours, minutes and seconds:

$$\text{days} = \left\lfloor \frac{s}{86{,}400} \right\rfloor, \quad \text{hours} = \left\lfloor \frac{s \bmod 86{,}400}{3{,}600} \right\rfloor, \quad \text{minutes} = \left\lfloor \frac{s \bmod 3{,}600}{60} \right\rfloor$$

with the remaining seconds last. Weeks are the days divided by 7, with the remainder in days. Total hours and total minutes are whole hours and whole minutes.

The calendar count works differently. It reads the event zone’s clock now and at the target, steps whole months forward from today’s date, then counts days, hours and minutes. A month from January 31 ends on February 28 (or 29), the last day of the shorter month.

Worked example: a launch livestream at 6:00 PM London time

A launch livestream starts at 6:00 PM in London on Thursday, February 25, 2027. The countdown is worked out at 12:00 PM UTC on Wednesday, September 23, 2026, which is 1:00 PM in London (British Summer Time) and 7:00 AM in Chicago.

1. Target in UTC. UK clocks go back on October 25, 2026, so on February 25 London is on GMT, UTC+00:00. 6:00 PM − 0 hours = 2027-02-25 18:00:00 UTC.
2. Seconds between now and then. From September 23 to February 25 is 155 days on the UTC calendar, and 18:00 − 12:00 is 6 hours: 155 × 86,400 + 6 × 3,600 = 13,413,600 seconds.
3. Days, hours, minutes, seconds. 13,413,600 ÷ 86,400 = 155 days with 21,600 seconds left over, which is 6 hours. The countdown reads 155 days 6 hours 0 minutes 0 seconds.
4. Weeks. 155 days = 22 × 7 + 1, so 22 weeks 1 day, plus 6 hours.
5. Totals. 13,413,600 ÷ 86,400 = 155.25 days; ÷ 3,600 = 3,726 hours; ÷ 60 = 223,560 minutes.
6. London’s calendar. From 1:00 PM on September 23 to 1:00 PM on February 23 is 5 months, then 2 days to February 25, then 5 hours to 6:00 PM: 5 months 2 days 5 hours. That is an hour short of the real 155 days 6 hours, because the clocks go back an hour on October 25 and that hour is lived through twice.
7. In Chicago. The livestream starts at 12:00 PM CST, UTC−06:00, on the same Thursday.

The milestone table then says when the countdown will read 100 days (Tuesday, November 17, 2026, 6:00 PM GMT, which is noon in Chicago) and 7 days (Thursday, February 18, 2027).

A spreadsheet can’t see time zones. On a computer set to London time, =DATE(2027,2,25)+TIME(18,0,0)-NOW() subtracts the two clock readings, so at that moment it gives 155.21 days (155 days 5 hours): the calendar count, not the real wait.

Days, weeks and hours until a date

• The big numbers are real elapsed time, in 24-hour days. They tick from your device’s clock every second. Announce time left reads them out for screen readers on request, and Pause live updates stops the ticking without changing the target.
• When it happens gives the target in its own time zone with its UTC offset and abbreviation, in your time zone, and in UTC.
• Weeks and days answers “how many weeks until …”: whole weeks, the days left over, then any hours.
• Total days, hours, minutes and seconds are the whole wait in one unit. Total days also shows how many calendar dates away the target is.
• Calendar in (place) counts months, days and clock time on the event’s own calendar, the way you would count on a wall calendar. It differs from the real time only when the clocks change in between.
• When the countdown shows each milestone lists the moments it will read 100 days, 30 days, 7 days, 1 day, 1 hour and so on, in the event’s time and yours, with a CSV download for a calendar or a to-do list.

Counting down to an event in another time zone

Pick the event’s time zone, not your own. A 6:00 PM start in London is noon in Chicago in winter, and a countdown that reads 6:00 PM in your own zone would run six hours too long. The page shows the target in both zones, so you can check the conversion at a glance.

Share link puts the event name, date, time and time zone in the web address. Everyone who opens it counts down to the same instant, and sees it in their own local time too. If you left the date or the zone blank, the link carries the date and zone that were used, so “5 p.m. today” in Chicago doesn’t become 5 p.m. somewhere else tomorrow.

Continue in the Time Zone Meeting Planner carries the same date, time and zone across, for seeing the moment in several cities at once.

What happens when daylight saving time changes before the date

The countdown itself is unaffected: it counts real seconds, and a clock change doesn’t add or remove any. What changes is how that time lines up with the calendar. When the clocks go back, the calendar count is an hour shorter than the real wait; when they go forward, an hour longer. The page names each change between now and the target and says which way it moves the count.

Two local times need a choice. A time inside the spring-forward gap, such as 2:30 AM in New York on Sunday, March 14, 2027, never happens; the countdown uses 3:30 AM EDT by default, the reading calendar files use, and lets you pick 1:30 AM EST instead. A time inside the fall-back hour, such as 1:30 AM in New York on Sunday, November 1, 2026, happens twice; the default is the first one (EDT), and the second is an hour later.

After the date: time since an event

Once the target passes, the headline switches to Time since, and every number counts up from the target: days since, weeks since, total hours since and the calendar count. If you watch it reach zero, screen readers hear that once. A past date typed on purpose, such as a quit date or an anniversary, works the same way. If you meant a future date, check the year.

Assumptions and limitations

• Offsets and clock changes come from your browser’s copy of the IANA time zone database. A target years ahead follows today’s rules, and governments sometimes change them at short notice, so check far-off countdowns again nearer the date.
• Leap seconds are not counted, as in computer clocks generally. When one is added to UTC before the target, the real wait is one second longer than shown.
• The countdown is only as right as your device’s clock. It reads that clock every second and whenever you return to the tab, so a background tab, which browsers may update only once a second or less, can’t make it drift.
• Dates from January 1, 1900 to December 31, 2200 are accepted. Clock changes are listed for spans of up to two years. Longer spans show only their net effect.
• Every day of the week counts. For working days only, use a business days calculator.

Common mistakes

• Entering the event in your own time zone. A webinar at “3 PM Eastern” needs America/New_York as its zone, not the zone of the computer you are using.
• Treating the calendar count as hours. Across a clock change, “5 months 2 days 5 hours” on the calendar and 155 days 6 hours of real time are both right. Use the big numbers for how long you actually wait.
• Typing an abbreviation. IST means India, Israel or Irish summer time; the page asks which place you mean instead of guessing. City names carry the full rules.
• Scheduling inside the skipped or repeated hour. A 2:30 AM target on a change night means different things in different apps. Move it, or pick the reading you mean when the page asks.