To add or subtract days from a date, simply select the base date from the first date picker and enter the number of days in the text box. Positive numbers will add days, while negative numbers will subtract days. Then, click on the 'Calculate' button to see the result.
To calculate the difference between two dates, choose the start date from the first date picker and the end date from the second date picker. Click on the 'Calculate Difference' button, and the number of days between the two dates will be displayed.