Date Add or Subtract Calculator
Move a date forward with a positive day adjustment or backward with a negative adjustment. The calculator operates on calendar dates and counts every day, including weekends and holidays.
Calendar-day arithmetic only. Day zero returns the start date, and every intervening date counts regardless of weekends or public holidays. It does not calculate business days, legal service deadlines, time zones, hours, or inclusive deadline rules.
Enter your scenario
Use the details that match your situation. Your estimate stays in this browser.
How this estimate works
- A positive adjustment moves the start date forward; a negative adjustment moves it backward; zero returns the same date.
- The calculation uses Gregorian calendar dates so month lengths and leap days are handled without treating every year as 365 days.
- Weekends and holidays are included. Use a jurisdiction-specific business-day tool when rules exclude them.
Official calendar references
- U.S. Naval Observatory: introduction to calendars and Gregorian leap-year rule
- NIST: timekeeping and clocks FAQ
The official references describe Gregorian calendar and timekeeping conventions. Deadline laws can impose separate inclusion, exclusion, and holiday rules.
Frequently asked questions
How do I subtract days from a date?
Enter the number of days as a negative value. For example, -14 moves the start date backward by 14 calendar days.
Are weekends included?
Yes. This calculator counts calendar days. Use the Japan business-days calculator when you need its weekday and holiday exclusions.