Add or subtract a number of days, weeks, or months from any date.
How to Add or Subtract Days from a Date
Choose your start date on daycalctools.com, select whether you want to add or subtract, enter the number of units, and choose the unit type (days, weeks, months, or years). Click Calculate and the resulting date is displayed instantly along with the day of the week it falls on.
The tool handles all calendar edge cases correctly. For example, adding one month to January 31 results in February 28 (or 29 in a leap year), since February does not have a 31st day. Adding days is always precise since each day is exactly 86,400 seconds. Adding months and years adjusts to the last valid day of the resulting month where needed.
When Would You Add or Subtract Days from a Date?
Date arithmetic is needed constantly in both personal and professional life:
- Invoice payment terms — Calculate the due date for a net-30 or net-60 invoice from the invoice date.
- Medical follow-ups — Find the date 14 days, 6 weeks, or 3 months after a procedure or prescription start date.
- Subscription renewals — Determine when a 30-day or annual subscription will renew based on the sign-up date.
- Warranty and return deadlines — Find out the last day to return a product or claim a warranty given a purchase date and policy period.
- Pregnancy due date estimation — Add 280 days (40 weeks) to the first day of the last menstrual period to estimate a due date.
- Scheduling tasks — Find out what date falls exactly N days before a deadline so you can schedule preparatory steps.
Frequently Asked Questions
Can I subtract days as well as add them?
Yes. Use the "Subtract" option in the selector to go backward from the start date. This is useful for finding a date a certain number of days before a deadline — for example, finding out when a notice must be sent given a legal deadline.
What is the difference between adding days and adding months?
Adding days always moves exactly that many 24-hour periods forward or backward, regardless of month boundaries. Adding months moves the month number by the specified amount, keeping the same day of the month where possible. For example, adding 1 month to March 15 gives April 15; but adding 1 month to March 31 gives April 30 because April has only 30 days.
How do I find the date 30 business days from today?
This tool calculates calendar days, not business days. To estimate 30 business days, multiply by approximately 1.4 (since a 5-day work week is 5/7 of a 7-day calendar week), giving roughly 42 calendar days. Then use this tool to add 42 days to today. You can verify the result by checking it in the
Working Days Calculator.
Does the tool show what day of the week the result falls on?
Yes. The result displays the full date including the day of the week (e.g., "Monday, June 9, 2025"). This is particularly useful when planning meetings or deadlines to immediately see if the date falls on a weekend.
Can I add weeks directly, or do I have to convert to days first?
You can add weeks directly by selecting "weeks" as the unit. This is equivalent to adding days × 7 but is more convenient for multi-week calculations. The tool supports days, weeks, months, and years as unit options.