Time tools
9 tools that run in your browser. Nothing to install, nothing uploaded.
Time and date utilities — timestamp conversion, duration maths — computed in your browser. The epoch converter is explicit about the two things that trip people up: telling a seconds timestamp from a milliseconds one, and showing everything in UTC so the answer reads the same for everyone rather than silently using your local timezone.
- Countdown TimerA countdown that stays accurate when the tab is in the background.
- Cron Expression ParserRead a cron expression in plain English and see when it next runs.
- Date Difference CalculatorDays, weeks, months and weekdays between two dates — counted the way people mean.
- Epoch / Unix Timestamp ConverterConvert a Unix timestamp to a date and back — in UTC, unambiguously.
- Interval / HIIT TimerRun work and rest intervals with a tone at each change.
- Meeting Timezone PlannerFind the hours a distributed team can actually meet.
- Alarm ClockSet an alarm for a clock time, with the caveats stated plainly.
- Pomodoro TimerFocus blocks and breaks, timed against the clock rather than counted.
- StopwatchA stopwatch with laps that does not drift in a background tab.
Seconds, milliseconds, and the ten-digit tell
The most common timestamp bug is a unit mismatch, and it is easy to spot once you know the shape. A Unix timestamp in seconds for any current date is ten digits; in milliseconds it is thirteen. Feed a seconds value to something expecting milliseconds and you land in January 1970; do the reverse and you land tens of thousands of years in the future. The converter states which unit it detected rather than guessing silently, and shows everything in UTC by default, so the answer reads the same for everyone instead of shifting with whichever timezone the reader happens to be in.
Date arithmetic does not work the way arithmetic does
Days are not uniform and months are not a fixed length, which makes several intuitive calculations wrong. Adding one month to 31 January has no correct answer without a convention. Daylight saving means some days have 23 or 25 hours, so a duration in days computed by dividing milliseconds is off by an hour twice a year. Leap years add a day on a rule most people remember only partially — divisible by four, except centuries, except those divisible by 400. The date tools here count whole calendar days the way people mean them and report weekday totals separately, which is usually the figure a working-days question actually wants.
Why a browser timer drifts, and what to do about it
A countdown built by adding a second on every tick accumulates error immediately, because browsers do not honour timer intervals precisely and throttle them hard in background tabs — often to once a minute — to save battery. A timer written that way can lose minutes over a long session and finish visibly late. The timers here store a target wall-clock time and compute the remaining interval against the system clock on each frame, so a tab that has been in the background wakes up with the correct time remaining rather than with however many ticks it managed to run.
Frequently asked questions
Is my timestamp in seconds or milliseconds?
Count the digits. For any current date, a Unix timestamp in seconds is ten digits and one in milliseconds is thirteen. The failure is easy to recognise once you know the shape: a seconds value read as milliseconds lands in January 1970, and a milliseconds value read as seconds lands tens of thousands of years in the future. The converter states which unit it detected rather than guessing quietly.
Why is everything shown in UTC?
So the answer means the same thing to everyone. A Unix timestamp is an absolute instant with no timezone attached, and rendering it in whatever local zone the reader happens to be in makes two people comparing the same value disagree. UTC also sidesteps daylight saving entirely, which is where most timestamp confusion originates — local time has days that are 23 and 25 hours long, and UTC does not.
Why does the countdown stay accurate when the tab is in the background?
Because it stores a target wall-clock time and recomputes the remaining interval against the system clock, rather than subtracting a second on each tick. Browsers throttle background timers hard — often to once a minute — to save battery, so a tick-counting timer drifts badly and can finish minutes late. Computing from the target means a tab that has been hidden for an hour wakes up with the correct time left.
How are months counted between two dates?
By calendar months, which is what people mean and what a raw division of milliseconds cannot give you, since months have different lengths. The date difference tool reports whole days as the primary figure because it is unambiguous, with months, weeks and weekday-only totals alongside — and weekdays is usually the number a working-days question actually wants.