Date & Time Calculators
Calendar arithmetic, working days, timesheets and time zones, with leap years, month ends and daylight saving handled explicitly.
Calculators
- Age Calculator
Exact age in years, months and days on any date, with leap-day birthdays handled.
- Days Between Dates Calculator
Days, weeks, months and years between two dates, with optional inclusive counting.
- Add or Subtract Dates Calculator
Add or subtract days, weeks, months and years, with end-of-month rules explained.
- Business Days Calculator
Count or add working days with your own weekend days and holidays.
- Time Duration Calculator
Add and subtract hours, minutes and seconds, including negative and 24+ hour totals.
- Timesheet Calculator
Weekly hours with unpaid breaks, overnight shifts and an overtime threshold you set.
- Time Zone Meeting Planner
Compare a meeting time across IANA time zones, with daylight-saving changes flagged.
- Countdown to a Date
Live countdown to a date and time in a chosen time zone.
Choosing a date or time calculator
Calendar questions look simple until a month ends on the 31st, a year is a leap year or the clocks change. Pick the tool that matches the question, and check how it treats those cases.
- How old is someone, exactly?
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Years, months and days on any date, with a choice of rule for February 29 birthdays in common years.
- How many days between two dates?
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Days Between Dates Calculator Business Days Calculator
Calendar days, weeks and months between dates, or working days with your own weekend days and holidays.
- What date is 90 days from now?
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Add or Subtract Dates Calculator
Adds or subtracts years, months, weeks and days, with a stated rule for month ends.
- How many hours did I work?
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Timesheet Calculator Time Duration Calculator
Shifts with unpaid breaks, overnight shifts and overtime thresholds, or any list of durations added and subtracted.
- When can people in different cities meet?
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Local times side by side, working-hours overlap and warnings near daylight-saving changes.
- How long until a date?
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Days, hours, minutes and seconds left until a moment in any time zone, updated live.
Have these to hand
- Both dates in full, including the year.
- Your employer’s or court’s holiday list; no holiday calendar is built in.
- Shift start and end times, and the length of unpaid breaks.
Mistakes that change the answer
- Forgetting whether the end date counts. A span that includes both the first and the last day is one day longer.
- Assuming month arithmetic is universal. January 31 plus one month is the last day of February under the usual clamping rule, and early March under the overflow rule some software uses.
- Planning across time zones with a fixed offset, which breaks when one place changes its clocks.
Related guides
- Scheduling across time zones and daylight saving time
Why a weekly meeting shifts by an hour for some attendees in March, April, September, October and November, what happens to times that are skipped or repeated, and which zone a recurring invite should follow.