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Date Calculator Guide
How to Use This Date Calculator
This free date calculator helps you add or subtract days, weeks, months, or years from any date. It also calculates the exact number of days between two dates, counts business days (weekdays), and tells you the day of the week for any date.
Common Use Cases
- Contract deadlines: Find the exact date 30, 60, or 90 days from a signing date.
- Project planning: Calculate delivery dates by adding weeks or months to a start date.
- Legal deadlines: Determine filing deadlines, notice periods, and statute of limitations dates.
- Travel planning: Count the days until your trip or calculate return dates.
- Pregnancy due dates: Add 40 weeks (280 days) from the last menstrual period.
- Financial calculations: Determine maturity dates, payment schedules, and interest periods.
- Warranty tracking: Find when a 1-year or 2-year warranty expires.
Business Days vs. Calendar Days
Calendar days include every day (Monday through Sunday), while business days count only weekdays (Monday through Friday). This distinction matters for contracts, shipping estimates, and legal deadlines. Our calculator shows both so you always have the information you need.
Adding Months and Years
When adding months, the calculator preserves the day of the month when possible. For example, adding 1 month to January 15 gives February 15. If the target month has fewer days (e.g., adding 1 month to January 31), the result is clamped to the last day of that month (February 28 or 29).
Leap Years
A leap year occurs every 4 years, except for years divisible by 100 -- unless also divisible by 400. This means 2024 and 2028 are leap years, but 2100 is not. The calculator handles leap years automatically in all calculations.