Date & Time Calculators
Calculate ages, dates, durations, working days and time zones.
Calculate exact age, age in total units and the next birthday from any date.
Open toolCalculate the exact duration between two dates in several useful formats.
Open toolAdd or subtract days, weeks, months or years from any calendar date.
Open toolCalculate elapsed hours, minutes and seconds between two times or date-times.
Open toolCount, add or subtract working days with custom weekends and holidays.
Open toolConvert a date and time between IANA time zones with DST support.
Open toolView a complete 12-month calendar for the current year or any year you choose.
Open toolTotal work hours across multiple time entries with unpaid breaks.
Open toolCount calendar days between two dates with inclusive or exclusive counting.
Open toolFind the weekday for any date in the Gregorian calendar.
Open toolFind the ISO week number, week-year and week dates for any date.
Open toolFind dates matching weekly and monthly recurring calendar patterns.
Open toolView a monthly calendar with weekday details and ISO week numbers.
Open toolConvert decimal numbers and Roman numerals in either direction.
Open toolCount down to any future date and time with live days, hours, minutes and seconds.
Open toolAdd or subtract hours, minutes and seconds from a starting time of day.
Open toolConvert between HH:MM:SS clock time and decimal hours for payroll and timesheets.
Open toolFind the best bedtimes or wake-up times based on 90-minute sleep cycles.
Open toolFind your western zodiac sign, element, ruling planet and birthstone from a birth date.
Open toolFind the Chinese zodiac animal, element and yin or yang for any birth year.
Open toolFind the moon phase, illumination and moon age for any calendar date.
Open toolFind the calendar and fiscal quarter for any date, with quarter start and end dates.
Open toolSee the current time in cities and time zones around the world at a glance.
Open toolPlan a meeting across time zones and download an event.ics calendar invite with a link and attendees.
Open toolCompare unlimited cities on one horizontal timeline and click any hour to convert the time across every zone.
Open toolFind good meeting times across multiple time zones with a working-hours overlap grid.
Open toolFind the ordinal day number of a date, days remaining and how much of the year has passed.
Open toolCalculate sunrise, sunset, solar noon and day length for any location and date.
Open toolFind the daylight saving clock change dates for any time zone and year.
Open toolConvert a clock time into a natural English phrase like quarter past ten.
Open toolDescribe the difference between two dates as a localized relative phrase such as tomorrow or 3 hours ago.
Open toolConvert an ISO date and time to Julian Day and Modified Julian Day values.
Open toolConvert a Gregorian date to Mayan Long Count, Tzolk'in and Haab values using the GMT correlation.
Open toolEstimate daylight hours from latitude and date using solar declination, including polar day and night.
Open toolAbout Date & Time Calculators
These date and time calculators handle the awkward maths of calendars: ages, date differences, durations, working days, week numbers and time-zone conversions. Instead of counting on your fingers or a paper calendar, you get an exact answer in seconds.
Use them to plan projects around business days, work out how many days until a deadline, convert a meeting time across time zones, or find the day of the week for any date. Each tool is precise and accounts for leap years and month lengths.
Everything runs in your browser, so your dates and plans stay private on your device.