Calendar days vs. business days
Calendar days count every day, including weekends and holidays: 10 calendar days from a Monday is the Thursday of the following week. Business days (working days) count only Monday to Friday: 10 business days from a Monday is the Monday two weeks later. Tick Skip US federal holidays to also jump over days such as Thanksgiving and Christmas (observed dates are used when a holiday falls on a weekend).
| Start | Add | Result |
|---|---|---|
| Monday, Oct 5, 2026 | 10 calendar days | Thursday, Oct 15, 2026 |
| Monday, Oct 5, 2026 | 10 business days | Monday, Oct 19, 2026 |
| Friday, Dec 18, 2026 | 5 business days, skipping holidays | Monday, Dec 28, 2026 |
How adding days works
For calendar days the calculator converts the date to a day number, adds your number, and converts back — so month lengths and leap years are always right. For business days it steps forward one day at a time, counting only working days, and lists any holidays it skipped. The start date itself is never counted: “1 business day after Friday” is Monday.
Examples of adding days
- Invoice due in 30 days: invoice date + 30 calendar days.
- Delivery in 5 working days: order date + 5 business days.
- Response required within 14 days: notice date + 14 calendar days — check whether a weekend deadline rolls over (see the Court Date Calculator for legal deadlines).
Need to go backwards? Use Subtract Days From Date. For weeks or months, use Add Weeks to Date or Add Months to Date, or the all-in-one Date Calculator.