Formula
result = start + (years, months) then + (weeks × 7 + days)
- Months are calendar months; if the day doesn't exist in the target month it moves to that month's last day.
Move by whole calendar months and years first, then by days.
Worked example
31 Jan 2024 + 1 month
- Start date
- 2024-01-31
- Operation
- Add
- Months
- 1
Date after adding
Thursday, 29 February 2024
ISO format: 2024-02-29
Total days moved: 29 days
How it works
Adding one month to 31 January 2024 gives 29 February 2024, the last day of February that year. Adding 30 days to the same date gives 1 March, because days are counted exactly rather than as months. That is why the order matters: years and months are applied first, then weeks and days.
The result includes the weekday and the total number of days moved. To compare two dates directly use Days Between Dates Calculator; to skip weekends and holidays when adding use the “add working days” option in the Working Days Calculator; for a resignation last day see Notice Period Calculator.
Assumptions and limits
- Gregorian calendar, years 1–9999.
Related tools
Days Between Dates CalculatorNumber of days, weeks, months and years between two dates, with an include-end-date option.Days Until CalculatorCountdown in days to a future date — or days since a past one — from today's date.Working Days CalculatorCount working days between two dates, or add working days to a date, with your own holidays.Notice Period CalculatorCareerYour last day of notice from the resignation date, in calendar or working days.Age CalculatorExact age in years, months and days from a date of birth, plus the next birthday.