Date Calculator

Usage Guide

The calculator has two modes. “Date difference” counts days, weeks, business days (Monday–Friday, both endpoints included), and a year/month/day breakdown between two dates. “Add/subtract” offsets a base date by years, months, or days — negative values go backwards — and handles month lengths and leap years automatically, clamping month-end dates: January 31 plus one month gives February 28 or 29.

Examples

• Count the business days from March 1 to June 30 to plan leave around a project.
• Subtract 100 days from today to find a warranty or anniversary start date.
• Add 3 months to January 31 and get April 30.

FAQ

• How are business days counted? Monday through Friday, including both the start and end dates; public holidays are not deducted.
• Why does Excel show a different number? Excel’s DATEDIF has special month-end rules; this tool clamps to the end of month.
• Does order matter? No. Dates are compared in the order you enter them, and reversed input is handled automatically.