Countdown Timer & Stopwatch
High-precision browser countdown timer and stopwatch derived from exact system clock timestamps.
How It Works & Methodology
JavaScript single-threaded event loops cause setInterval ticks to drift under browser tab throttling or heavy CPU load. This tool derives all elapsed and remaining intervals from absolute Date.now() timestamps, guaranteeing zero time drift even if the tab sleeps or lags.
Key Assumptions & Scope:
- Timestamps are referenced from local high-resolution clock (Date.now()).
- Countdown durations are bounded between 1 second and 24 hours (86,400 seconds).
- All intervals and timers are cleanly disconnected and cleared upon unmount.
Frequently Asked Questions
Why does this timer not drift when backgrounded?
Instead of subtracting 1 second per tick, the timer stores the initial start timestamp and computes the exact difference against Date.now() on every render.
Can I record lap splits on the stopwatch?
Yes. Clicking the Lap button while the stopwatch is running records the instantaneous split timestamp in the lap history table.
What is the maximum countdown duration?
The countdown timer supports durations from 1 second up to 24 hours (23 hours, 59 minutes, 59 seconds).