Date and time calculators
Age, day counts, business days, timesheets, leap year, sunrise, moon phase, and calendar arithmetic in this browser.
16 tools
In this group
Age and date difference start the group. Add civil months with date add. Business days skip Saturday and Sunday. Timesheet and work hours total clocks. Leap year tests the Gregorian rule. Sunrise and sunset use the NOAA zenith. Moon phase uses a simple synodic month. ISO week numbers and a year table are here. Time zones live under datetime converters.
- Age Calculator Civil calendar age in the local timezone of this device. Leave As of blank to use today.
- Business Days Calculator Count Monday to Friday between two dates. Optional holidays you type. No public-holiday API.
- Year Calendar Leap flag, weekday of 1 January, ISO week count, and a 12-month table of lengths and start weekdays.
- Date Countdown Days remaining until a date, or days since if the target is past. Also years/months/days.
- Add or Subtract Days Add or subtract years, months, weeks, and days. Month ends clamp (31 Jan + 1 month is 28 or 29 Feb).
- Date Difference Calculator Days between two local calendar dates. If the end is before the start, the result is signed negative.
- Day of Week Calculator Weekday, ISO weekday (Monday = 1), day of year, and leap-year flag.
- Hours Minutes Seconds Calculator Convert duration parts, decimal hours, or total seconds into HH:MM:SS and the other totals.
- Leap Year Calculator Check whether a year is a Gregorian leap year. Divisible by 4, except centuries that are not divisible by 400. The page also reports February length and year length.
- Moon Phase Calculator Approximate phase name, illumination, and age from a civil date using a simple synodic-month model. Not a rise/set almanac and not weather.
- Sunrise Sunset Calculator Sunrise, sunset, and solar noon from latitude, longitude, and date. NOAA solar calculator with zenith 90.833 degrees. Named cities use that city's IANA offset for the date, including DST. Custom uses the minutes you type. Not a weather forecast.
- Time Card Calculator Time card total from in/out lines. Same engine as timesheet, labeled for time-clock searches.
- Time Duration Calculator Add two durations or subtract the second from the first. Hours may go past 24.
- Timesheet Calculator Sum clock-in/out lines into total, regular, and overtime hours. Optional unpaid minutes per line.
- Week Number Calculator ISO-8601 week number and ISO year. Weeks start Monday. Week 1 contains 4 January.
- Work Hours Calculator Net hours for a clock-in/out pair, unpaid break, optional day multiplier, and overtime over a daily threshold.