UMSO Help Desk
If you miss a deadline, your grade won't be affected, and you don't need to change your deadlines. You'll still be able to earn a Course Certificate once you complete all your work.
If you submit a peer-reviewed assignment after your personalized deadline, you might not get enough peer reviews. If you need more peer reviews, you can post in the forums asking for more peer feedback.
If you miss 2 deadlines in a row or miss a deadline by 2 weeks, you'll see an option that says Reset my deadlines. Even if you don't see that option yet, you can still submit work - there is no penalty for a "late" assignment.
Note: Since Coursera courses no longer run on sessions, you don't need to worry about waiting for a session to start or switching sessions.