Resetting dates in Course Site can be done through the "Course Reset" function after you copy your previous course.
Access Course Reset:
Navigate to your course page in Course Site.
Click "More" in the top navigation
From the dropdown menu, select "Course reuse".
On the Course reuse page, click the "Reset" tab.
Choose Reset Options:
Course start date: Set a new start date for the course.
Initiate Reset:
Once you've selected the desired reset options, click the "Reset course" button at the bottom of the page.
Moodle will show a confirmation screen listing the actions that will be performed. Review this carefully.
If you're sure about the reset, click "Continue".