How Date Calculations Work
Date calculations help you find the difference between two dates or determine a future/past date by adding or subtracting time units. Our calculator handles months with different lengths, leap years, and business day calculations automatically.
Business Days vs. Calendar Days
Business days (also called working days or weekdays) exclude Saturdays and Sundays. This calculator counts business days between two dates. For example, one calendar week has 7 calendar days but only 5 business days.
Leap Years
A leap year occurs every 4 years (with exceptions for century years not divisible by 400). Leap years have 366 days instead of 365, with February having 29 days. This calculator automatically accounts for leap years.
Common Date Calculations
- 90 days from today: Often used for project deadlines and financial quarters
- 30/60/90 day periods: Standard business intervals
- 180 days: Half a year, used for many legal and financial deadlines
- 365 days: One full year from any date
Frequently Asked Questions
Does this include the start date? No — the day count starts from the day after the start date. For example, January 1 to January 2 = 1 day.
How are business days calculated? Business days exclude Saturdays and Sundays. Public holidays are not excluded as they vary by country and region.
How does adding months work? Adding 1 month to January 31 gives February 28 (or 29 in a leap year), since February doesn't have 31 days.