5 Calculators
Date & Time
Days until a date, dates from today, ages, elapsed time and time unit conversions, counted on the Gregorian calendar.
These calculators count time on the calendar and the clock: how many days until a date, what date falls a number of days from today, how old someone is, how long passed between two times, and how many weeks or hours are in a longer span. They count on the Gregorian calendar, the one in civil use almost everywhere, with its leap years every four years except century years not divisible by 400.
Counting days is where small conventions matter, and each page says which one it uses: whether the start date counts as day one, whether a span ends at midnight or at the same clock time, and how a month is treated when the day you start from does not exist in the month you land in, such as 31 January plus one month.
The time unit converter treats a year as the mean Gregorian year of 365.2425 days unless you pick a common year of 365 days or a leap year of 366, and it shows which one was used beside every answer. A month is one twelfth of the year chosen.
Start here
- What date is 90 days from today?
- Use the date calculator with today as the start and add 90 days. It also gives the weekday of the result.Date Calculator: Days From Today, or Days Ago
- How many weeks are in a year?
- The time unit converter gives 52.1775 weeks for the mean Gregorian year, and about 52.14 for a 365-day year. Both are shown, because both answers are in common use.Time Unit Converter: Weeks in a Year, Days, Hours and Seconds
How these calculators fit together
Counting to and from a date
The days until calculator counts down from today to Christmas, New Year, Valentine’s Day, Halloween, US Thanksgiving or any date, not counting the start day. The date calculator adds or subtracts days, weeks, months or years from a start date and shows the weekday it lands on. Both read today from your own device when the page opens.
Days Until Christmas Calculator (and Any Other Date)Date Calculator: Days From Today, or Days Ago
Ages and durations
The age calculator gives an age in years, months and days from a birth date, counted the way a birthday is: by whole calendar months. The time duration calculator gives the hours and minutes between two clock times, reading an end time earlier than the start as the next day, and takes off a break.
Age Calculator by Date of BirthTime Duration Calculator (Hours and Minutes Between Two Times)
Converting units of time
Seconds, minutes, hours, days, weeks, months and years, in any direction, with the year length stated.
Time Unit Converter: Weeks in a Year, Days, Hours and Seconds
What these tools leave out
- Dates are counted in your own calendar day. Time zones and daylight saving changes are not applied unless a page says it handles them.
- Historical dates before the Gregorian calendar was adopted in a given country are counted as if it had always applied.
- Business-day counts need a holiday calendar for a particular place, which these tools do not assume.
All Calculators
Works out an age from a date of birth in years, months and days, counted by whole calendar months, with totals in months, days and weeks, the next birthday and the weekday of birth.
Adds or subtracts days, weeks, calendar months or calendar years from today or any start date and gives the resulting date, its weekday, the calendar days between and the day of the year.
Counts the days from today, read from the reader's own device, to Christmas, New Year's Day, Valentine's Day, Halloween, US Thanksgiving or any chosen date, and shows the span in weeks, months, weekdays and hours.
Works out the hours and minutes between two clock times, reading an earlier end time as the next day, subtracts a break, and gives the result in minutes, decimal hours and 12-hour clock form.
Converts amounts of time between milliseconds, seconds, minutes, hours, days, weeks, months, years, decades and centuries, with the year taken as 365.2425, 365 or 366 days and all three answers shown.