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- Add or subtract any number of years, months, weeks and days from a start date to get the new date and its weekday.
- Years and months are applied first, then weeks and days, which is how most people count calendar time.
- If the start day does not exist in the new month, such as January 31 plus one month, the last day of that month is used.
- The count includes weekends and holidays. For business days only, use the working days calculator.
How to use the add days to date calculator
Pick the start date
It starts on today, and you can change it to any date.
Choose Add or Subtract
Add moves forward in time, and Subtract moves back.
Enter the amounts
Fill in years, months, weeks and days. You can use one box or all four, and blank boxes count as zero.
Read the new date
The result shows the full date, its weekday, the days between and the steps used.
How adding time to a date works
Days are easy to add because every day has the same length. Months are harder because they have 28, 29, 30 or 31 days. So the calculator moves by whole months on the calendar first. Adding one month to March 15 gives April 15, whatever the length of March. Only then does it add the weeks and days as a plain count of days.
Order of the steps
Step 1: move the date by the years and months
Step 2: if that day does not exist, use the last day of the month
Step 3: move the date by weeks × 7 + days
Result = the date after step 3, with its weekday
Subtracting follows the same order, but moves backward.
What happens at the end of a month
Month ends cause most surprises. January 31 plus one month cannot be February 31, so the calculator gives the last day of February, which is February 29 in 2024 and February 28 in 2025. The same rule applies to leap days: February 29, 2024 plus one year is February 28, 2025, because 2025 has no February 29.
Worked examples
Example 1: 30 days from a date
Start on Saturday, October 24, 2026 and add 30 days.
October has 31 days, so 7 days reach October 31 and 23 more reach November 23.
Example 2: a month-end start
Add one month to January 31, 2024.
The last day of the month is used when the exact day does not exist.
Example 3: subtracting time
Go back 1 year, 2 months and 10 days from October 24, 2026.
Years and months come off first, then the days.
Example 4: 100 days ahead
Add 100 days to October 24, 2026.
A hundred days is just over 14 weeks.
Days in each month
Month lengths
Why a month is not always the same number of days.
These different lengths are why the calculator adds months on the calendar instead of as 30 days each.
Common day counts
Handy approximate conversions.
For exact results, use the months and years boxes instead of counting days.
Where an add days to date calculator helps
Deadlines and due dates
Find the date 14, 30 or 90 days after an invoice, order or contract date.
Returns and warranties
See when a 30-day return window or a one-year warranty ends.
Courses and study plans
Work out the finish date of a 12-week course or a 100-day challenge.
Trips and events
Count forward or backward from a flight, wedding or holiday date.
To count the days between two dates, use the date difference calculator. For weekdays only, try the working days calculator, and to check the weekday of a single date use the day of week calculator. Legal and contract deadlines can have their own counting rules, so check the wording of your agreement.
Add days to date calculator FAQ
How do I add days to a date?
Enter the start date, leave Add selected and type the number of days. The calculator returns the new date and its weekday.
What is 30 days from today?
It depends on the date today. Leave the start date on today and enter 30 days to see it. For example, 30 days after October 24, 2026 is Monday, November 23, 2026.
How do I subtract days from a date?
Choose Subtract and enter the amount. The calculator counts backward, so 20 days before January 10, 2026 is Sunday, December 21, 2025.
What happens if I add a month to January 31?
The result is the last day of the next month, because February has no 31st. In 2024 that is February 29, and in 2025 it is February 28.
Does the calculator skip weekends or holidays?
No. It counts every calendar day. To count business days only, use the working days calculator.
Can I add years, months and days together?
Yes. Fill in as many boxes as you need. The calculator applies years and months first and then weeks and days.