How to add days to an existing date value
To create a column that displays date values that are greater than the date values in another column, complete the following steps.
1 Select a column. The calculated column appears to the right of the selected column. Choose New Computed Column. Calculation appears.
2 In Column Label, type a name for the calculated column. For example, type Forecast Shipping Date.
3 In Enter Expression, type the letter A. A drop-down list appears, displaying functions that begin with A.
5 For the first argument, type a left bracket ([) and select the date column from the drop-down list. For example, select Order Date.
7 Validate the expression and choose OK. The calculated column appears in the report. For every value in the Order Date column, the calculated column displays a date seven days later than the order date.