Time & Date Calculators
Dates and durations, counted precisely. Days between two dates, business days, adding weeks or months, exact age, time arithmetic and countdowns to the moments that matter.
25 calculators
Most used
- Age CalculatorWork out an exact age in years, months and days, with totals in weeks, days and hours and a countdown to the next birthday.
- Date CalculatorFind the date that falls a set number of days, weeks, months or years before or after any date, in calendar or business days.
- Days Between DatesCount the exact number of days between two dates and see the gap in years, months, weeks and business days.
- Time Zone ConverterConvert a date and time into any number of world time zones, with daylight saving time handled and an hour-by-hour meeting planner.
Date calculators 7
- Business Days CalculatorCount the working days between two dates, with weekends and observed US federal holidays taken out and listed.
- Date CalculatorFind the date that falls a set number of days, weeks, months or years before or after any date, in calendar or business days.
- Days Between DatesCount the exact number of days between two dates and see the gap in years, months, weeks and business days.
- Day of the Week CalculatorFind which day of the week any date falls on and follow the Doomsday rule or Zeller's congruence step by step.
- Days UntilSee how many days are left until Christmas, a holiday or your own date — with weeks, months, workdays and weekends in between.
- Leap Year CalculatorCheck whether a year is a leap year, see the divisibility rule applied step by step, or list all leap years between two years.
- Week Number CalculatorFind the ISO week number of any date, the Monday and Sunday of that week, and every week of the year listed with its dates.
Time arithmetic 4
- Add Time CalculatorAdd or subtract days, hours and minutes from a clock time to find what time it will be, including the day it lands on.
- Hours and Minutes CalculatorPaste or type a list of times like 7:45 and get the total in hours and minutes, decimal hours and optional pay.
- Time CalculatorAdd, subtract, multiply or divide lengths of time given in days, hours, minutes and seconds, with the conversion shown.
- Time Duration CalculatorMeasure the time between two clock times or two date-and-time points, with overnight spans and daylight saving changes handled.
Age 4
- Age CalculatorWork out an exact age in years, months and days, with totals in weeks, days and hours and a countdown to the next birthday.
- Age CheckerCheck whether a person meets a minimum age on a given date and find the exact day they reach it.
- Age DifferenceCompare two birth dates to get the exact age gap in years, months and days, how the age ratio changes, and when one person was twice as old.
- Birthday CalculatorCount down to your next birthday and see the weekday you were born, your half-birthday and the weekday of each upcoming birthday.
Timers, clocks & sun 4
- Countdown TimerCount down live to any date and time, give the event a name, and share a link that shows the same countdown to anyone.
- StopwatchTime anything to the hundredth of a second, record laps and splits, and copy the results, using the mouse or keyboard shortcuts.
- Sunrise & Sunset CalculatorGet sunrise, sunset, solar noon, day length and twilight times for any city or coordinates on any date, worked out with NOAA's solar equations.
- Time Zone ConverterConvert a date and time into any number of world time zones, with daylight saving time handled and an hour-by-hour meeting planner.
Calendar, zodiac & moon 6
- Chinese ZodiacEnter a birth date to get the Chinese zodiac animal, element and yin-yang, using the real Lunar New Year date for that year — not just the Gregorian year.
- Easter DateEnter a year to get Western and Orthodox Easter Sunday, the movable feasts that depend on them, and the step-by-step computus behind the date.
- Julian DateConvert between calendar dates and Julian Dates (JD and MJD), plus the YYDDD ordinal dates stamped on packaging and military paperwork.
- Moon PhasePick a date, time and time zone to see the moon's phase, how much of the disk is lit, its age in days and the dates of the coming full and new moons.
- Printable CalendarBuild a clean month or full-year calendar with US federal holidays, choose Sunday or Monday starts and week numbers, then print it or save it as a PDF.
- Zodiac SignEnter your birth date, and optionally the time and time zone, to find your sun sign from the Sun's actual position — reliable even on cusp days.
Guides
- How Leap Years Work: The Rule, the Reason and the ExceptionsA year is a leap year if it is divisible by 4, unless it is a century year not divisible by 400. Learn why the rule exists and how it affects dates and pay.
- How to Calculate Your Age in Days, Weeks and HoursYour age in days is 365 times your full years, plus one for each leap day you have lived through, plus the days since your last birthday. Here is the method.
- How to Calculate Business Days Between Dates (Excluding Holidays)Business days are weekdays minus holidays. Learn a fast hand method, how to add business days to a deadline, which holidays to skip and the 2026 counts.
- How to Count Days Between Two Dates (Inclusive or Exclusive)Subtract the earlier date from the later one to get elapsed days, and add one if both end dates count. Learn the hand method, the fencepost trap and real uses.
- How to Find the Day of the Week for Any Date (Doomsday and Zeller)Find the weekday of any past or future date with two methods: Conway's Doomsday rule for mental math and Zeller's congruence for a reliable formula.
- ISO Week Numbers Explained: How to Find the Week Number of a DateISO weeks run Monday to Sunday, and week 1 is the week with the year's first Thursday. Learn the formula, 53-week years and how US week numbers differ.