Countdown Timer Calculator
Create a live countdown to any future date and time — watch days, hours, minutes, and seconds tick down in real time for any event or deadline.
Your Target Event
Enter a target date to start the countdown.
How It Works
The calculator reads your target date and time, then subtracts the current timestamp every second using a live JavaScript timer. The millisecond difference is broken into days, hours, minutes, and seconds. If the target has already passed, the timer switches to counting up — showing how long ago the event occurred.
Formula
Time remaining = Target datetime − Current datetime (ms). Days = floor(ms ÷ 86,400,000). Hours = floor(remainder ÷ 3,600,000). Minutes and seconds follow the same pattern.
Timer behaviour
- Future date
- Counts down — days/hours/minutes/seconds remaining
- Past date
- Counts up — shows elapsed time since the event
- Same day
- Shows hours, minutes, and seconds to/from the target time
- Accuracy
- Reads system clock every second — does not drift over time
Frequently Asked Questions
Does the countdown update live?
Yes — the timer refreshes every second automatically in your browser. There is no need to reload the page.
What happens when the target date passes?
The display switches from a countdown to a count-up, showing how much time has elapsed since the target moment. It works symmetrically in both directions.
Can I set a countdown to a specific time of day?
Yes — enter both a target date and a target time (hour and minute). The countdown will tick down to that exact moment, accurate to the second.
Is the timer accurate?
The timer is accurate to within 1 second. It reads the system clock on every tick rather than counting internally, so it won't drift even if left running for hours.