The tool uses your browser's built-in Date objects to perform the calculations. For duration, it calculates the difference in milliseconds between the two dates and converts it to days. For adding/subtracting, it uses the `setDate` method, which correctly handles month and year rollovers.

1. Choose your mode: 'Duration Between Dates' or 'Add/Subtract Days'.
2. For 'Duration', pick a start and end date to see the time between them.
3. For 'Add/Subtract', pick a start date, choose 'Add' or 'Subtract', and enter the number of days.

• Calculating your age in days.
• Figuring out the deadline for a 90-day project.
• Finding out how many days are left until your next vacation.

• Dual Modes: Flexible calculations for duration or date addition/subtraction.
• Clear Duration Results: Calculates the duration in both total days and in weeks + days.
• Handles Leap Years: All calculations automatically account for leap years.
• Simple Interface: Uses user-friendly date pickers for easy input.

Date arithmetic is complex because of varying month lengths and leap years. By leveraging the browser's built-in date engine, this tool can perform these calculations accurately and instantly without you having to worry about the details.

All calculations and data processing for this tool are performed locally in your browser. We do not send any of your data to our servers, ensuring your information remains private and secure.