Is there a bug in Due Date calculations?

When trying to set an Action Rule to change the status of a ticket from Waiting on Client to Follow Up if we have not received a response 1 business day after the ticket's due date, I noticed that all the Waiting on Client tickets have a due date of March 26, 2024 (5 business days from today). The due date tool tip says, "The default Due Date is calculated by adding the 'Due Time' of the specified Priority to the Open Date." We have found this to not be true however.

For example, we have a ticket that was opened on March 7, with a medium priority (5 days) but the due date (for this one, and ALL of our Waiting On Client tickets, regardless of open date) is March 26. Something is broken there.

We host WHD locally on a Windows Server 2012 box, and are on 12.8.1 - Build # of WHD. Is there an issue with time syncing on the server, or is this a bug in 12.8.1?

Due date screenshot