In a column of type formula, the function DATE_ADD () displays a date which is the addition of a date of a column of date type and a number X of days.
DATE_ADD (Date column, 3)
the first parameter is the exact name of a date column.
The second parameter is an integer that corresponds to the number of days I want to add. This number can be positive or negative.
DATE_ADD (Send quote, 3)
I added 3 days to my quote submission date.
DATE_ADD (Customer Delivery, -4)
I subtract 4 days from my date Customer Delivery.