Hi @rbostrom 
Thank You for posting your question. Please check out this Guide: How do I change the start and end dates for a course?. Some schools do not allow their instructors to change course start/end dates on their own. If this is the case for you, then you'll need to reach out to your school's local Canvas administrator to see if that person would be able to change the dates for you. I hope this helps, Bob. Please let Community members know if you have any other questions about this...thanks!
