Ideas for implementing a separate resource calendar

Summary:

We are currently using an organization calendar collected from EBS with 5 working days and 3 shifts of 8 hours each.

The new business requirement is to implement a separate calendar with: 4 working days per week 2 shifts per day 10 hours per shift . However, this requirement should apply only to WIP/resource planning activities.

We tested creating a new calendar with the above setup and assigning it to the inventory organization, but this is impacting sales order ship dates, which we want to avoid. The expectation is to have this calendar considered only for resource planning without affecting order promising or any other modules.