Calendar dates
Explore calendar dates tools with formulas, input guidance and worked examples.
Date difference calculator
Count the calendar days between two dates, with leap years handled automatically and no timezone shift.
Open toolWeeks Between Dates Calculator
Count complete weeks and remaining calendar days between two dates.
Open toolMonths Between Dates Calculator
Count complete calendar months between dates using an explicit end-of-month anniversary rule.
Open toolYears Between Dates Calculator
Count complete calendar years between dates, with February 29 anniversaries clamped to February 28.
Open toolAdd Months Calculator
Add or subtract calendar months and handle shorter destination months explicitly.
Open toolAdd Years Calculator
Add or subtract calendar years, including leap-day dates.
Open toolWeekday Calculator
Find the day of the week for a past or future Gregorian calendar date.
Open toolDay Of Year Calculator
Find a date’s day number within its year, accounting for leap years.
Open toolWeek Number Calculator
Find the ISO week number, ISO week-year and weekday for a calendar date.
Open toolIso Week To Date Calculator
Convert an ISO week-year, week number and weekday into a calendar date.
Open toolLeap Year Calculator
Check whether a Gregorian year is a leap year and whether it has 365 or 366 days.
Open toolDays In Month Calculator
Find the number of days in a month for the chosen Gregorian year.
Open toolJulian Date Calculator
Convert a timestamp to a UTC-based Julian date using the stated civil-time approximation.
Open tool