Add Days to Date or Subtract: Date Calculator

Use this add days to date calculator whenever you need to know which date falls a set amount of time before or after another one. Enter a starting date, choose add or subtract, and pick a unit: days, weeks, months, years or business days. The result date appears immediately with its weekday, its ISO week number and how far it is from today.

Find a future or past date in seconds

1. Enter the start date, such as an invoice date, a purchase date or today.
2. Choose whether to add or subtract.
3. Type the amount and select the unit: days, weeks, months, years or business days.
4. Read the result date, including the day of the week and ISO week.
5. Check the distance from today to see whether the date is close or still far off.

Because the weekday is shown right next to the result, you can spot at a glance when a deadline lands on a Saturday or Sunday and plan around it.

How month-end dates are handled

Adding months is trickier than adding days, because months have different lengths. Tempoo follows the rule most people and most software expect: if the starting day does not exist in the target month, the result moves to the last day of that month. So January 31 plus one month gives February 28, or February 29 in a leap year, and March 31 plus one month gives April 30. Adding years from February 29 works the same way and lands on February 28 in a common year.

If you need an exact number of days instead, for example a 30-day return window, choose days rather than months. “One month” and “30 days” often produce different dates.

Business-day mode

In business-day mode, the calculator skips Saturdays, Sundays and the US federal holidays configured on the site, such as Thanksgiving, Independence Day and Christmas Day. That makes it useful for anything described as “within 10 business days”. State and local holidays, as well as company-specific days off, are not skipped, so double-check those if they apply to you.

Practical uses

• Payment terms: work out the due date for net 30 or net 60 invoices.
• Shipping and delivery: estimate when an order should arrive if it ships in a set number of business days.
• Deadlines: find the last day to respond, file or submit something.
• 90-day rules: calculate when a 90-day period ends, for travel stays, trial periods or probation.
• Warranties and returns: see when a one-year warranty or a 30-day return window runs out.
• Due dates: count forward in weeks for appointments or milestones.

Tips for accurate results

Check whether the period you are calculating starts on the same day or the next day. Many legal and contractual deadlines start counting the day after an event, so you may need to add one extra day. Also confirm whether the rule speaks of calendar days or business days, since 10 calendar days and 10 business days can be almost a week apart. Once you have the date, you can create a countdown to it on tempoo and add it to your calendar so you do not miss it.