Countdown Calculator
Live countdown timer to any date with preset events, real-time ticking display, and time-since mode for past dates.
Countdown calculator
Live — updates every secondHow the countdown is measured
- Δt
- Difference in milliseconds between the two moments
- targetms
- UNIX timestamp of the target date in the chosen time zone
- nowms
- Current UNIX timestamp from the browser clock
- Total seconds = ⌊|Δt| / 1000⌋
- Total minutes = ⌊|Δt| / 60 000⌋
- Total hours = ⌊|Δt| / 3 600 000⌋
- Total days = ⌊|Δt| / 86 400 000⌋
- Business days = total days minus weekend days in the span
Time zones. Pick the time zone that matters for your event. "New Year in Tokyo" and "New Year in New York" are 14 hours apart even though both say January 1st 00:00 locally. The countdown picks the chosen zone's moment, then subtracts your browser's current UTC time.
Daylight saving. Spring-forward and fall-back transitions shift the countdown by an hour for affected zones — the calculator reflects this automatically because it works in absolute UTC milliseconds, not local wall-clock time.
Leap seconds. The browser clock smears or ignores leap seconds depending on the OS. Differences are at most one second per year and are not surfaced in the countdown.
Business days. Counted as Monday through Friday in the target's time zone — public holidays are not excluded. Use the business-days calculator if you need holiday-aware counts.
Examples
How It Works
How it works: The calculator subtracts the current time from your target date every second, breaking the difference into days, hours, minutes, and seconds. The display updates in real time using a one-second interval timer.
Past dates: If your target date is in the past, the calculator automatically switches to "Time since" mode, showing how long ago the event occurred. This makes it useful for tracking both upcoming events and elapsed time.
Quick presets let you instantly set popular dates like New Year's Day, Christmas, Valentine's Day, Halloween, and Independence Day. Each preset automatically selects the next upcoming occurrence of that holiday.
Tips & Best Practices
Frequently Asked Questions
Does the countdown update in real time?
Yes, the display updates every second automatically. Days, hours, minutes, and seconds all tick down live without needing to refresh the page.
What happens when the countdown reaches zero?
The calculator switches to 'Time since' mode and begins counting up, showing how long ago the target date/time passed.
Which time zone does the countdown use?
The countdown uses your browser's local time zone. The target date and time are interpreted in your local time.