Calendar and Weeks
Weekday, week number, week calendar, day of year, leap year, quarter and workday calculators
Day of Week Calculator
Find the weekday for any date, including birth dates and future dates, with ISO day number, ISO week-year, day of year, weekend status and leap-year context.
Day of Year Calculator
Find the ordinal day number for any date, convert a day number back to a date, and see year progress, days remaining, ISO week and leap-year context.
Week Number Calculator
Find the ISO week number for any date, convert an ISO week number to its Monday-to-Sunday date range, and compare with a Sunday-start US week number.
Week Calendar
Show every ISO week in a selected year with Monday-Sunday date ranges, quarter labels, current-week highlighting and table copy.
Leap Year Calculator
Check whether a year is a leap year under the Gregorian calendar rule, see whether February 29 exists, and list leap years in a selected range.
Quarter Calculator
Find the calendar or fiscal quarter for a date, quarter start and end dates, progress, total days and weekday-only business days.
Business Days Calculator
Count business days between two dates or add and subtract business days with weekends and optional U.S. federal holidays excluded.