When is the SQL for Default value in a DFF triggered (on Shipment page) ?

Summary:

We need to create a DFF on the shipment page to store today's date. For this we are using the Default Type as "SQL" & the query as "select sysdate from Dual". But the value is not showing up on the frontend. (Even tried using 'Trunc' with sysdate, just in case if timestamp is causing any issues. )

So, just wanted to understand at what point does this query gets triggered to fetch & store the value on the DFF? Is it during creation, or saving of the Shipment?

Any suggestions please.

Content (please ensure you mask any confidential information):

Version (include the version you are using, if applicable):