Date and Time Calculators
29 calculators
Calendar arithmetic: adding days or working days, countdowns, ages in days, business-day spans and time-of-day sums. Leap years and month lengths are handled, but local public holidays are not built in, and results crossing a daylight-saving change inherit whatever your device reports. Anything contractual should be checked against the calendar that governs it.
- Add Time Calculator Add or subtract two durations and get the result as HH:MM:SS plus decimal hours for payroll.
- Baby Age Calculator Track a baby’s age in weeks, days and months from their date of birth.
- Birthday Calculator Find your next birthday, how many days away it is, and how old you will turn.
- Birthday Countdown Calculator Count down the days, weeks and hours until a birthday.
- Business Days Calculator Count weekdays between two dates or add weekdays to a date; public holidays are not excluded.
- Conception Date Calculator — Estimate from Due Date Enter an estimated due date and average cycle length to estimate conception and last-period dates. A calendar estimate, not an exact date derived from a birthday.
- Countdown Calculator The start date is editable and defaults to the user’s local calendar date. Future spans are positive and past spans negative.
- Countdown Days Calculator Count elapsed days, approximate workdays and rest days between two dates.
- Date Difference Calculator Calculate the number of days, weeks, months and years between two dates.
- Day of the Week Calculator Find out which day of the week any date falls on.
- Days Until Christmas Calculator See how many days are left until Christmas, with the weekday it falls on this year.
- Days Until New Year Calculator Count down the days remaining until 1 January.
- Epoch Converter Convert between Unix timestamps and human-readable dates in UTC and local time.
- Time Format Converter Convert a clock time between 12-hour and 24-hour notation in both directions at once.
- Hours Calculator Calculate hours worked between two times, with an unpaid break deducted.
- Leap Year Calculator Check whether a year is a leap year and see how many days it contains.
- Military Time Converter Convert between 24-hour military time and standard 12-hour AM/PM time.
- Minutes to Hours Converter Convert minutes into hours and minutes, with seconds and decimal hours.
- Moon Phase Calculator Calculate the moon phase and illumination for any date.
- Retirement Countdown Calculator Count down the days, weeks and working days until you reach retirement age.
- Sunrise and Sunset Calculator Estimate sunrise, sunset and daylight hours for any date, latitude and longitude.
- Time Card Calculator Add up a week of working hours and calculate regular pay, overtime and gross wages.
- Time Duration Calculator Calculate the duration between two times in hours, minutes and seconds.
- Time Zone Converter Convert a wall-clock time from one UTC offset to another, with the day shift shown explicitly.
- Timesheet Calculator Add up hours worked from clock-in and clock-out times and get gross pay, including overtime over 40 hours.
- Week Number Calculator Find the ISO week number and week of the year for any date.
- Weeks Calculator Convert between weeks, days, hours, minutes and seconds.
- Work Days Calculator Count the working days between two dates, excluding weekends and holidays.
- Zodiac Sign Calculator This calculator maps a valid birth date to a Western sun sign using a fixed month-and-day lookup table evaluated in UTC. It does not calculate an astronomical chart; the same month and day always return the same sign here. For entertainment, not a scientific assessment.
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Calendar arithmetic and elapsed time are related but different. A month can have different lengths, a weekday count is not automatically a holiday-aware work calendar, and a Unix timestamp identifies an instant rather than a local calendar label. Choose the time convention before entering the dates.
Compare dates or move to a new date
Use date addition to move by days or calendar months. For an interval, distinguish elapsed totals from a calendar breakdown into years, months and remaining days. Review whether the start or end date is included in a count.
Convert between calendar labels and computer time
Convert an existing timestamp to its UTC date, or enter a date and time to obtain seconds and milliseconds since the epoch. A leap-year check answers a calendar-rule question; a time-zone converter needs a separate zone convention.
Read inclusion and zone rules
Two tools can disagree without either being a duplicate: they may count included dates differently or return average-length months instead of complete calendar months. Check the page’s UTC, local-time and holiday assumptions before comparing results.