Time, counted carefully

See how long is left — and what the calendar actually does. Countdown clocks, kitchen timers, and date math that document leap years, month-end overflow, and time zones instead of hiding them.

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Quick countdown: pick a preset above. For a custom target, use the Countdown Timer.

Countdown tools

Countdown Timer

Count down to any date and time, with pause, presets and a shareable link.

How Long Until

See days, hours, minutes and seconds left until a date or clock time.

Days Until

Count the days, weeks and months left until a target date.

Time tools

Online Timer

Set hours, minutes and seconds and run a simple timer.

Stopwatch

Start, pause and record laps with a millisecond display.

Time Calculator

Add or subtract hours, minutes and seconds across several durations.

Hours From Now

Find the exact date and time a number of hours from now.

Hours Ago

Find the exact date and time a number of hours ago.

Minutes From Now

Find the exact date and time a number of minutes from now.

Date tools

Date Calculator

Find the difference between dates, or add days, weeks, months, years or business days.

Age Calculator

Work out years, months and days between a birth date and a target date.

Time Zone Converter

Convert a date and time between IANA time zones, including daylight saving.

Days From Today

Find the date a number of days from today.

Weeks From Today

Find the date a number of weeks from today.

Months From Today

Find the date a number of months from today, with the month-end rule stated.

Years From Today

Find the date a number of years from today.

Calendar tools

Day of the Year

Find which day of the year a date falls on.

Days Left in the Year

Count how many days remain in the current year.

Weeks Left in the Year

Count how many weeks remain in the current year.

Sleep Calculator

Estimate bedtimes and wake times from 90-minute sleep cycles.

Event countdowns

Thanksgiving

Countdown to the fourth Thursday of November (US).

Easter

Countdown to Easter Sunday, worked out by computus.

All event countdowns

Browse every recurring event countdown in one place.

How Long Until also has a page for every minute of the day — 1,440 minute pages — from 12:00 AM to 11:59 PM.

How it works

Pick a tool that matches the question: remaining time, elapsed time, or calendar arithmetic.
Enter dates and times. Invalid values are rejected instead of being silently coerced.
Live tools subtract from a stored timestamp so the number stays honest if the tab sleeps.

Why these tools

Date math fails in predictable ways: February 31, daylight saving gaps, birthdays on leap days. Each calculator states the rule it uses. There are no accounts, no social publishing features, and no invented usage statistics.

Questions

Do these calculators use my local time?

Interactive tools read the current time from your browser and convert wall times with IANA time zones. The server does not assume its own zone is yours.

Why can a countdown jump after I leave a tab open?

Browsers slow background timers. These tools store a target timestamp and subtract the current time on each tick, so returning to the tab corrects the display.

Is an account required?

No. Preferences stay in local storage on your device. Nothing here is a signed-in product or a social publisher.