Add or Subtract Dates Calculator — Date Arithmetic
Add or subtract days, weeks, months, and years from any date to find the resulting date. Use our Days Calculator to count days between dates, or the Date Calculator for more options.
How to Add or Subtract Dates
- Enter your starting date.
- Choose whether to add or subtract.
- Enter the number of years, months, weeks, and/or days.
- Click Calculate to see the resulting date.
- The result shows the full date including the day of the week.
Formula
Result Date = Start Date + Years + Months + (Weeks x 7 + Days)
Years and months are added first (calendar arithmetic)
Then days and weeks are added (simple day count)
Example
Start Date: January 15, 2025
Add: 2 months and 10 days
+ 2 months = March 15, 2025
+ 10 days = March 25, 2025
Result: Tuesday, March 25, 2025
Common Date Additions Reference
| From Jan 1, 2025 | Add | Result |
|---|---|---|
| Jan 1, 2025 | 30 days | January 31, 2025 |
| Jan 1, 2025 | 60 days | March 2, 2025 |
| Jan 1, 2025 | 90 days | April 1, 2025 |
| Jan 1, 2025 | 6 months | July 1, 2025 |
| Jan 1, 2025 | 1 year | January 1, 2026 |
| Jan 1, 2025 | 18 months | July 1, 2026 |
Frequently Asked Questions
What happens when adding months to the 31st?
If the resulting month has fewer days, the date rolls to the next month. For example, January 31 + 1 month = March 3 (since February has 28 days).
Does this account for leap years?
Yes. Adding 1 year from Feb 29, 2024 gives Feb 28, 2025 (since 2025 is not a leap year).
Can I subtract more than the start date?
Yes. Subtracting beyond the start date will give you a date in the past, which is perfectly valid.
Are business days considered?
No, this calculator counts all calendar days including weekends and holidays. Use our Working Days Calculator for business day calculations.
What is the order of operations?
Years are added first, then months, then the total of weeks and days. This order matters because month lengths vary.