QB Issue Resolution:

Go to “Edit”>”Preferences” then click on “Time & Expenses” then click on the “Company Preference” tab.
Select “Saturday” as “First day of Work Week”.

I hope this helps. Let us know by clicking on the “Thumbs Up Yes” or “Thumbs Down No” button by “Was this answer helpful”?

Resolution for Issue 'Changing the Week Start Day in the Timesheet' available: Yes (Solved).
Source: Intuit Community forum.

Changing the Week Start Day in the Timesheet: this issue or error code is a known issue in Quickbooks Online (QBO) and/or Quickbooks. Support for this issue is available either by self-service or paid support options. Experts are available to resolve your Quickbooks issue to ensure minimal downtime and continue running your business. First try to resolve the issue yourself by looking for a resolution described below. If it is a complex issue or you are unable to solve the issue, you may contact us by clicking here or by using other support options.

Support for timesheet
Quickbooks Repair Pro will resolve it efficiently and affordably. Guaranteed resolution of your issue, or you pay nothing!

Error Recovery for timesheet [Canada]
E-Tech is the #1 Quickbooks data migration and Conversion service provider.

Get 50% off Quickbooks Online

Click Here for 50% off!

Additional Support Options: