Date Calculator
Find exact days between two dates, or add/subtract days from any date to find deadlines, milestones, and expiration dates.
Inputs
- Date Operation
- Starting Date
- Number of Days
- Direction
- Target Ending Date
Worked examples
90-Day Legal or Notice Period
You sign an agreement on October 1 and must track an exact 90 calendar day response deadline. Result: December 30, 2026 (90 Calendar Days).
Target Date = Start Date + 90 calendar days. Includes 64 business weekdays and 26 weekend days.
Days Between Summer Project Milestones
A product sprint begins June 1, 2026 and ships on September 15, 2026. Result: 106 Calendar Days (76 Business Days).
Span = 15 weeks + 1 day = 106 total calendar days. 76 workdays excluding Saturdays and Sundays.
Frequently asked questions
Does this date calculator account for leap years?
Yes. The calculation uses full ISO astronomical calendar arithmetic and correctly accounts for 366 days in leap years and the 29 days of February.
What qualifies as a business day?
A business day is standardly counted as Monday through Friday. Public statutory holidays (like Labor Day or Thanksgiving) vary by jurisdiction and company.
What are common date calculation deadlines?
Typical commercial deadlines include 30-day invoice payment terms (Net 30), 60-day warranty windows, 90-day probationary review periods, and 180-day passport expiration rules.