Yes and No.
You are required to stay on schedule with assignments and login multiple times per week. Some classes may have several due dates each week; others may require work once per week. You do have the flexibility of choosing the time of day or night you want to log on to the Internet to work on your assignments, but you must complete it and "turn it in" by the specified date and time.
Additionally, in most online classes, instructors will host live classroom sessions at specific times throughout the week. You should make every attempt to attend these sessions as they provide an opportunity to interact with your instructor, dive deeper into the course materials, and meet with your classmates.