Change format date for Completion Course Certificate template

Summary:

Hello all,

We're modifying the data template for the Completion Certificate Course using BI Publisher.
We need to change "COMPLATION DATE" data format.
Analyzing CourseCompletionCertificate_Data_AllFields.xml file we discovered that the completion date format is the following:

<COMPLETION_DATE>2020-07-15T17:50:49.061+00:00</COMPLETION_DATE>

We need to change it and to have just data in the following format: DD-MM-YYYY.
We tried to insert new format into xml file and we saved it, but it didn't work.
If we do the certificate download, we still see this format → 2020-07-15T17:50:49.061+00:00 .

Is there someone who can help us or give us some suggestions?