Category
Time
Work with dates, times and zones: convert Unix timestamps, compare cities on the world clock, compute date differences and working days, split a date range into chunks, and build recurring schedules. These tools handle the calendar's sharp edges — DST shifts, leap years, month-length quirks — so you don't have to.
D-Day Calculator
Count the days between two dates, or the countdown to a target date.
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Stopwatch & Timer
A precise stopwatch with laps and a countdown timer with an alarm.
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Unix Timestamp Converter
Convert Unix timestamps to dates and dates back to timestamps.
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Timezone Converter
Convert a date and time between any two world timezones, including DST.
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World Clock
See several time zones side by side with live updates and offset differences from your local time.
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Date Calculator
Add or subtract years, months, weeks, days, and business days from any date — or find the difference between two dates.
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Pomodoro Timer
Run focused 25-minute work sessions and short / long breaks, with a circular timer, sound alerts, and a daily counter.
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Duration Calculator
Add and subtract time durations in hours, minutes and seconds — get the total as h:m:s plus decimal hours, total minutes and total seconds.
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Working Days Calculator
Count the business days between two dates — pick which weekdays count as weekend and paste a list of holidays to exclude.
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Sunrise & Sunset Calculator
Compute sunrise, sunset, solar noon, and all three twilight phases for any latitude, longitude, and date — using the NOAA solar algorithm.
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ISO 8601 Week Calculator
Convert any date to its ISO week number (and back) — get the Monday-start / Sunday-end of that week, ISO year, day-of-year, and how many weeks the year has.
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Lunar Calendar Converter
Convert between solar (Gregorian) and East Asian lunisolar calendar dates. Returns zodiac animal and ganzhi (heavenly-stem/earthly-branch) year name.
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Moon Phase Calculator (Illumination, Age, Next Full/New)
Pick any date and get the lunar phase name, illumination percentage, age in days, an SVG of the current shape, and the next new and full moon dates.
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Specialized tools26
Tools for narrower, more technical jobs: particular file formats, standards and professional fields. They work like every other tool here, entirely in your browser.
TZif Zoneinfo File Inspector
Open a compiled zoneinfo file in your browser: header, local time types, every transition, leap seconds and the POSIX TZ footer, parsed.
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Time Difference Calculator
Calculate the exact difference between two date-times, broken down into days, hours, minutes, and seconds.
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Day of Year · ISO Week · Julian Day
Show day of year, ISO 8601 week, quarter, Julian day, Unix timestamp, leap-year status, and year progress for any date.
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Duration Formatter
Convert a duration between human ("1h 30m"), clock (1:30:00), ISO 8601 (PT1H30M), and raw seconds/minutes/hours/days.
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Date Format Converter
Type any date (ISO, RFC, Unix epoch, locale) and see it rendered in 14+ standard formats side by side.
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Cron Next Runs
Type a 5-field cron expression and see the next N times it will fire — local time, including weekday + day-of-month dual semantics.
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Recurring Event Calculator
Pick a pattern (weekly, every Nth weekday of the month, on the same day of month, every N days) and see the next N actual dates.
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Date Range Splitter
Split a date range into N equal intervals — get the start/end of each chunk or just the boundary dates between them.
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Easter Date Calculator
Compute Easter Sunday for any year using the standard Gregorian computus — or the Julian (Eastern Orthodox) variant.
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Quarter Calculator
For any date, get the calendar and fiscal quarter (configurable fiscal-year start), days into and left in it, and the quarter's start and end dates.
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Meeting Time Finder Across Timezones
Add timezones with each participant's working hours, see the 24-hour overlap grid, and read the best meeting slot in everyone's local time.
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Add Business Hours to a Date
Add N working hours to a start datetime — skip weekends and holidays, respect a per-day work window, get the landing timestamp and a per-day breakdown.
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Birthday Countdown
Type a birthdate, get a live ticking countdown to the next birthday — plus exact age, days since born, hours lived, and the rare golden birthday year.
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Calendar Heatmap from Date List
Paste a list of YYYY-MM-DD dates (with optional counts) and render a GitHub-style yearly heatmap — palette, week start, streaks, hover counts.
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Julian Day Converter
Convert between a Gregorian date and a Julian Day (JD), Julian Day Number (JDN), Modified Julian Day (MJD), Reduced/Truncated JD, and Unix timestamp.
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Relative Time Formatter
Format any past or future date as 2 hours ago, in 3 days or last month — in 12 locales and three styles, with numeric: auto phrasing.
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Weekday Finder
Look up the day of the week for any date — supports multiple dates at once, multilingual day names, ISO week numbers, day-of-year, and leap-year flag.
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GPS Time, TAI and Leap Second Converter
Convert UTC to GPS week and time of week, TAI and the GPS−UTC offset, with every leap second since 1972 listed.
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Unix Time Precision Converter
Convert a timestamp between seconds, milliseconds, microseconds, and nanoseconds since Unix epoch.
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Sidereal Time Calculator (GMST, LMST, JD)
Convert any UTC moment to Greenwich and Local Sidereal Time, Julian Date, Modified Julian Date and Earth rotation angle — for telescope alignment.
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BPM / Tempo to Delay & Note Length Calculator
Convert a musical tempo (BPM) to note durations in milliseconds — straight, dotted and triplet — for whole, half, quarter, 8th, 16th, 32nd, 64th notes.
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Moonrise, Moonset & Moon Position
Moonrise, moonset and transit times for any place and date, plus the Moon's altitude, azimuth, distance and illuminated fraction at a chosen moment.
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Equation of Time & Sundial Correction Calculator
Compute the Equation of Time — the gap between mean and apparent solar time — for any date, plus your local solar noon and the sundial offset.
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Epoch Time Converter (Unix, FILETIME, Excel)
Convert one moment in time between 11 epoch formats — Unix seconds and ms, NTP, Windows FILETIME, .NET Ticks, Mac HFS+, Excel serial, ISO 8601.
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Biorhythm Calculator (Daily Cycle Chart)
Plot the classic biorhythm cycles — physical (23), emotional (28), intellectual (33 days) — with a ±15-day chart and a critical-day list.
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Planet Birthday Calculator (Age on Mars, Venus, Jupiter…)
How old are you on Mercury, Mars, Saturn or Pluto? Enter your birth date and see your age plus next-birthday countdown for every planet in the Solar System.
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