Four collisions worth settling before you click
The shelf has 25 pages. Most mix-ups happen inside four clusters. Settle the cluster, then open the row.
Now, or later
World Clock, Time Zone Comparison, Timezone Converter
World Clock and Time Zone Comparison both read the current moment. Comparison lines the cities up and prints the offset plus the daylight-saving state. The world clock adds a check for a shared working hour. Timezone Converter is the other job. Hand the converter a date and a time in one zone, and the page prints the slot in another. A meeting next Thursday belongs on the converter.
Weekends, or holidays too
Days Calculator, Business Days Calculator
Days Calculator counts the days between two dates. Working-days mode drops weekends and leaves public holidays in the total. Business Days Calculator drops weekends and, once you pick a country, the holidays on the selected calendar. A shop open Saturday matches neither default. Read the inclusion setting on the business-days page before the number goes into a contract.
Span, invoice, or age
Time Between Dates, Duration Calculator, Age Calculator
Time Between Dates prints years, months, days, hours, and minutes. Duration Calculator strips breaks and non-working hours, rounds to a billing increment, and offers decimal hours or an ISO 8601 duration. Age Calculator starts from a birth date and adds a birthday countdown. Project length is the first. A timesheet line is the second. A birthday is the third.
Ten digits, or thirteen
Unix Timestamp Converter, Timestamp Converter
Unix Timestamp Converter accepts seconds, milliseconds, microseconds, and nanoseconds. Ten digits, thirteen, sixteen, nineteen. Timestamp Converter swaps Unix seconds, Unix milliseconds, ISO 8601, and a written date. Microseconds and nanoseconds are the Unix page. A 13-digit JavaScript value dropped into a seconds field is how the year lands in the far future.
Every date and time tool on the shelf
25 pages. Each row says what you bring, what comes back, and where the page refuses to go further.
Live clocks
4These four read the current moment. None of them moves a meeting to next Thursday.
What Time Is Now
Nothing. The page reads the device clock.
Local time, GMT/UTC, the zone name, and a Unix timestamp, ticking each second. A wrong device clock makes the whole row wrong.
UTC Time
Optional: a UTC slot you want in your own zone.
Live UTC, your offset on a 24-hour dial, and copy-out as ISO 8601, HTTP date, or Unix. Leap seconds get a short note here. The long version is the UTC essay.
World Clock
Cities.
Current time, offsets, and which places share a working hour. Daylight saving is applied. The reading is now, not a date you type.
Time Zone Comparison
A short list of cities.
The same moment, side by side, with the offset and daylight-saving state on every row. Still the current moment.
Move a value
5A zone-to-zone slot, a Unix integer, a written date, or a raw count of seconds.
Timezone Converter
A date, a time, a source zone, a target zone.
The same slot in the other zone. Zones come from the Olson list, and daylight saving follows the date you picked, not today.
Unix Timestamp Converter
Seconds, milliseconds, microseconds, or nanoseconds. Or a date, going the other way.
Ten, thirteen, sixteen, or nineteen digits. JavaScript stores milliseconds. Feed a 13-digit value to the seconds field and the year jumps centuries.
Timestamp Converter
Unix seconds, Unix milliseconds, an ISO 8601 string, or a written date.
Swaps those four. Microseconds and nanoseconds belong on the Unix page.
Date Format Converter
A date string, and the pattern you believe the string uses.
ISO 8601, US, European, or a custom pattern. The parsed date is shown, because 03/04/2026 is March or April depending on the pattern.
Time Converter
A count and a unit.
Seconds, minutes, hours, days, weeks, months, years. Months use an average length. A real calendar month belongs on Add Time to Date.
Count a span
6Two dates go in. The length that comes out is a different length on each page.
Days Calculator
Two dates.
The day count. Working-days mode drops weekends. Public holidays stay in the total.
Business Days Calculator
Two dates, and a country if holidays should leave the count.
Weekends out, plus holidays for the country you select. A shop open on Saturday matches neither default. Check the end-date inclusion setting before a contract uses the number.
Time Between Dates
Two dates, with times if you have them.
Years, months, days, hours, and minutes. No billing round. No holiday calendar.
Duration Calculator
Two date-times, the breaks, and the hours you do not bill.
Breaks and non-working hours stripped, then a round to your billing increment. Copy decimal hours or ISO 8601. An invoice span, not an age.
Age Calculator
A birth date.
Years, months, days, and a countdown to the next birthday. A project length belongs on Time Between Dates.
Weekday Calculator
One date.
The weekday name. Spot-check a date you already know before you trust a birthday from 1900.
Step off a date
2Start from one date and move by a unit you name. Month-end is the row to read twice.
Add Time to Date
A start, plus years, months, days, hours, minutes, or seconds.
The later date. 31 January plus one month is calendar arithmetic, not 31 days. Read the result before the date lands in a notice period.
Subtract Time from Date
A start, and the same units subtracted.
The earlier date. The month-end caution runs backwards too.
One year, one grid
1Not a timer and not a national holiday list.
Calendar
A year.
Twelve months, US federal holidays, a weekend count, and a business-day total for the year you pick. A UK bank holiday is not on this grid.
Clocks you start
5They run in this browser. A closed tab is not a backup clock.
Stopwatch
A start press, then lap presses.
Elapsed time and laps. The page keeps timing if you switch tabs. Closing the browser ends the session. A certified finish line is a different instrument.
Countdown Timer
An end, or a length. A theme if you want one.
A count toward an event, with sound and a shareable setup. Closing the browser stops the count.
Timer with Alerts
A label, a length, a tone.
A browser notification and phone vibration while the tab stays open. Close the tab and the countdown dies. Refresh restores the saved length, sitting at Ready, not the seconds you had left.
Interval Timer
Work, rest, rounds, and a get-ready count. Or a Tabata, HIIT, EMOM, or boxing preset.
Tones or voice. Keep the tab in front. A hidden tab gets throttled: the clock catches up, the cue arrives late. A locked phone stays quiet.
Pomodoro Timer
A start press on the 25-minute block.
A work interval, then a break. Useful as a focus log. Client hours belong on the work tracker.
Hours already spent
2One records as you go. One reads a paste. Neither one uploads the log.
Work Time Tracker
Projects, plus start and stop. Or a manual row if you forgot.
A timesheet export. Entries live in this browser. Clear site data and the log leaves with them. Export first.
Time Log Analyzer
A pasted log.
Hours by task, day, and category, charted. The paste stays in the tab. A messy paste produces a messy chart.
09:00 in Karachi is midnight in New York
Monday 6 April 2026, 09:00 in Karachi. Pakistan stays on UTC+5 all year. On that date London is on British Summer Time, UTC+1. New York is on Eastern Daylight Time, UTC−4. Tokyo is on Japan Standard Time, UTC+9, with no daylight saving.
So 09:00 Karachi is 04:00 UTC.
09:00 Karachi
Looks fine on a local clock- London05:00
- New York00:00
- Tokyo13:00
18:00 Karachi
London and New York overlap- London14:00
- New York09:00
- Tokyo22:00
Shift the same meeting to 18:00 Karachi and London moves to 14:00, New York to 09:00, Tokyo to 22:00. London and New York now share an office hour. Tokyo does not. There is no hour on this date when Karachi, London, New York, and Tokyo all sit inside 09:00 to 17:00. Someone stays late, or the invite drops a city.
Type 6 April 2026, 09:00, source Karachi, target New York, on the timezone converter. The page should print midnight. A result of 09:00 means both selectors are the same zone.
A browser tab is a bad place to store a promise
The failures below are ordinary. They show up after someone has already copied the number into a contract, a ticket, or a kitchen timer.
- Months on the unit converter
- Time Converter treats a month as an average length. A due date one calendar month out belongs on Add Time to Date. Read 31 January plus one month before the date goes into a notice.
- Holidays on the year grid
- Calendar marks US federal holidays for the year on screen. A bank holiday outside the US federal list is absent. Business days for another country belong on the business days calculator, with the country selected.
- The timesheet in this browser
- Work Time Tracker keeps entries on this device. Clear site data and the log is gone. Export the timesheet before you clear. Time Log Analyzer never uploads the paste, and a broken paste charts whatever landed in the box.
- Refresh on the alert timer
- Timer with Alerts stores the label, the length, and the tone. The seconds still running are not stored. Refresh and you are back at Ready, on the saved length.
- A Pomodoro is not a timesheet
- The Pomodoro page is built around a 25-minute work block and a break. Session stats are a focus log. Billable hours belong on the work time tracker.
- Closing the browser
- Countdown Timer, Stopwatch, Interval Timer, and Timer with Alerts all live in the open page. Close the browser and the session ends. None of them is a substitute for a clock that has to ring while the laptop sleeps.
After the result looks wrong
Why did 03/04/2026 land on the wrong day?
Date Format Converter shows the parsed date next to the converted string. US order reads 03/04/2026 as 3 April. European order reads the same characters as 3 March. Copy the ISO string only after the parsed date is the day you meant.
The Unix year is 1970, or somewhere past 50000.
Count the digits. Ten digits are seconds. Thirteen are milliseconds. Sixteen are microseconds. Nineteen are nanoseconds. A millisecond value read as seconds jumps centuries ahead. A seconds value read as milliseconds sits near January 1970. Unix Timestamp Converter takes all four lengths. Timestamp Converter stops at milliseconds, and also takes ISO 8601.
Business days and the days calculator disagree.
Working-days mode on Days Calculator removes weekends and keeps public holidays. Business Days Calculator removes weekends and the holidays for the country you select. The business-days page also has an inclusion choice for the end date. A team that works Saturday matches neither default week.
The alarm rang late, or never.
Timer with Alerts ends when the tab closes. A hidden tab is slowed by the browser, so the tone waits for the next tick the browser allows. Interval Timer has the same limit, and a locked phone stays quiet. Refresh on Timer with Alerts restores the saved length at Ready. The seconds already counted are not stored.
Where do leap seconds get explained?
On the UTC Time tool, in short. The UTC essay is the offset table and the cases that trip code. This guide will not repeat the essay.
The UTC essay is the long version
UTC Time is the live clock and the short account of leap seconds. The essay next door is the offset table and the places the standard trips code. Sleep cycles, loan dates, and half-life sit in other categories. A Unix integer starts on the Unix page. A count of working days starts on business days, with the country selected before you trust the total.