Hi Choquel,
Have you tried configuring the 'first-day-of-week' option in GIM to set this? This option setting defines what day is considered to be the start of the week. By default it is set as 1 (Sunday). So, if you set this to a value of 2, you can have future reports compliant with ISO 8601 standard. This option change will take effect upon the next completion of Job_MaintainGIM.
Best Regards,
Neil