⏱ Date & Time

13 browser-local tools · page 1 of 1

Date & Time. Calendars are full of edge cases and these pages exist to get them right: days between two dates with a working-day count, an exact age in years, months and days, the ISO week a date falls in with its year boundary handled, a weekday finder that walks to the next date matching a rule, a printable month grid, epoch timestamps in both directions with seconds and milliseconds distinguished, and a live countdown.

13 tools on this shelf · 13 listed below

📅Date & Age CalculatorDays between any two dates, add or subtract days, exact age in years-months-days, working days and days to your next birthday. ⏱Unix Timestamp ConverterEpoch to date and back, with seconds/millisecond auto-detection, ISO 8601, your local zone and a live ticking clock. 🌍Time Zone PlannerCompare up to eight cities hour by hour and find the call time that works for everyone — real IANA offsets and daylight saving, computed in the browser. ⏳Countdown TimerA live seconds-accurate countdown to any date — exams, flights, launches, birthdays — that keeps counting up after it passes. 🗓️Week NumberThe week number the standard actually defines — first week contains a Thursday, weeks start Monday — plus day-of-year, days left, and the reverse lookup from W-number to dates. 🗓️Calendar GridA printable month grid for any month in 240 years — Monday or Sunday start, ISO week numbers down the side, generated from calendar arithmetic and nothing else. 🎵MetronomeA precise click track from the browser\u2019s own audio clock — 40 to 208 BPM, accented first beat, 2/3/4/6 per bar, and the Andante-to-Presto names the sheet music promises. ⏱️Stopwatch & LapsA lap-split stopwatch whose time comes from the system clock, not a ticking counter — background-tab throttling cannot make it drift a single millisecond. 🌙Moon PhaseThe Moon\u2019s age, phase name and lit fraction for any date from the mean synodic month — with the ±1 day accuracy honestly stated. ✝️Easter DateEaster Sunday for any year from the 6th-century algorithm the Church still uses — Western and Orthodox dates side by side, with the intermediate golden number and epact. 📅Weekday FinderWhat weekday is 14 March 2027? A calendar-correct answer for any date, plus every year your birthday lands on a Saturday. ⏳Days Between DatesHow many days until the deadline — plain, or weekends excluded, with the ISO week span and the y-m-d breakdown. 🍅Pomodoro TimerRun proper pomodoro sessions — 25 minutes of work, 5 of rest, a long break every fourth — with the countdown kept on the system clock, so a throttled tab loses nothing.

How these tools work

Date arithmetic is done on real Gregorian dates rather than by dividing millisecond differences, because a day is not always 86,400 seconds where daylight saving is in force — that is the classic bug in code like this, and the pages count calendar days instead. Timers, stopwatches and the pomodoro use the browser clock you can see in the address bar, and the moon phase and Easter computus are the published algorithms, printed with their assumptions.

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