Hello @Luca_Lattarini
How to format the data will depend on the original format of the data.
for eg If your original date format looks like this "2022-09-13 10:00:00".
Then you can do something like this:
split(myData," ")[0]
The output will be 2022-09-13
Refer to this page for all functions:
Data Prep Mapping Functions | Adobe Experience Platform
You can also use the date_part function
eg: date_part(date("2022-09-13 12:55:12"), "MM")
The output will be 09