Free add or subtract date calculator
Add Months to a Date—or Subtract Days, Weeks & Years
Add or subtract calendar months, days, weeks, and years from any date and see the exact result, weekday, and ISO date.
Date Tools
Browser based
Runs on the current page
Copy-ready
Use the output where you work
No sign-in
Open the tool and get moving
Date tool
Date Calculator
Add or subtract days, weeks, months, and years from a date using real calendar month lengths.
Result date
Friday, September 4, 2026
ISO date
2026-09-04
Weekday
Friday
Calendar distance
0 years, 1 month, 0 days
Day shift
31 days
Calendar-safe date math
How to add months to a date
Choose a start date, keep Add to date selected, and enter the number of months. The calculator moves by real calendar months, then shows the exact result date, weekday, calendar distance, and ISO date. Switch the operation to subtract months or combine years, weeks, and days in the same calculation.
1. Choose a date
Select any past, present, or future start date—or use today.
2. Set the change
Choose add or subtract, then enter months, years, weeks, or days.
3. Read the result
Copy the calculated date or use its weekday and ISO date in your workflow.
A calendar month is not always 30 days
Months contain 28, 29, 30, or 31 days. When the destination month is shorter, the calculator uses the last valid day instead of rolling unexpectedly into another month. That makes the result useful for renewals, contracts, appointments, and project dates.
| Start date | Change | Result rule |
|---|---|---|
| January 31 | Add 1 month | February 28 or 29 |
| March 31 | Subtract 1 month | February 28 or 29 |
| February 29 | Add 1 year | February 28 in a common year |
Choose the right date tool
Use this calculator when you need to move one date forward or backward. To measure a gap, use the days between dates calculator. For work-week deadlines, use the business days calculator and review our guide to calendar days versus business days.
Built for the task
Age, dates, weekdays, and business-day answers.
Calculate age, date differences, weekdays, ISO weeks, business days, and Unix timestamps.
More tools
Continue with related date tools.
Timestamp Converter
Convert Unix timestamps in seconds or milliseconds into local time, UTC, and ISO strings.
Age Calculator
Calculate exact age in years, months, and days with total days lived and next birthday countdown.
Days Between Dates
Find the exact days, weeks, months, and years between two calendar dates.
Business Days Calculator
Count Monday to Friday business days between two dates and separate weekend days.
Day of Week Calculator
Find what day of the week any date falls on, plus day-of-year and ISO week details.
Week Number Calculator
Calculate the ISO week number, ISO week-year, weekday number, and weeks in the year.
FAQ
Date Calculator questions.
How do I add months to a date?
Choose a start date, select Add to date, and enter the number of calendar months. The result updates immediately with the full date, weekday, and ISO date.
Can I add months to dates like January 31?
Yes. The calculator respects real month lengths and clamps month-end results to the last valid day of the target month.
Is adding one month the same as adding 30 days?
No. A calendar month can contain 28, 29, 30, or 31 days. This calculator moves by calendar months instead of treating every month as a fixed number of days.
Can this subtract dates too?
Yes. Switch the operation from add to subtract and enter the years, months, weeks, or days to remove.
Can I calculate a date before or after today?
Yes. Select Use today, choose Add to date or Subtract from date, and enter any combination of years, months, weeks, and days.
Custom software