Scriptcase provides a very useful macro for manipulating dates, which is a very laborious process, however with the use of the sc_date macro (Increments and Decrement Dates), it is much simpler, example:

sc_date (Date, format, operator, D, M, A)

date - Date field containing the date to be modified
format - Formatting in which the date field is
operator - "" for increment and "-" for decrement
D - Number of days to increase or decrease
M - Number of months to increase or decrease
A - Number of years to increase or decrease

E.g.1:

{datanasc} = sc_data ({datanasc}, "dd/mm/aaaa", " ", 30, 0, 0);

E.g.2:

$nova_data = sc_data ({datanasc}, "aaaa-mm-dd", "-", 15, 3, 2);

E.g.3:

{dt_inclusao} = sc_data (date('Ymd'), "aaaammdd", "-", 0, 1, 1);

Tip:

To make sure the date format, before using the function, put a command in its formula:
echo "form_data =". {date field name};

Run the application and see the correct format.