Date & Days Calculator

How the Date & Days Calculator Works

This tool offers two modes for working with dates. Days Between Dates tells you the exact number of calendar days, business days (Monday–Friday), weeks, and months separating any two dates. Add / Subtract Days lets you start from any date and offset it by a given number of days to find the resulting date.

Business Days vs. Calendar Days

Business days exclude Saturdays and Sundays. This is useful for calculating delivery estimates, project timelines, or payment terms (e.g., “Net 30 business days”). Note that public holidays are not excluded from the business day count, since holidays vary widely by country and region.

Common Uses

• Counting down days until a wedding, vacation, or deadline
• Calculating the number of working days in a project timeline
• Finding a future or past date (e.g., “What date is 90 days from today?”)
• Determining how many days between two historical events
• Tracking age in days or weeks (especially for pregnancies)

Leap Year Handling

This calculator fully accounts for leap years. A year is a leap year if it is divisible by 4, except for years divisible by 100 — unless also divisible by 400. So 2000 was a leap year, but 1900 was not.