Exact student registration appointment dates and times are posted directly on their Student Center in the box titled, "Enrollment Information". To determine the exact time and day, click on "details" in this box. Below is a screen shot image of the Student Center.
All students receive an email from the Registrar's office stating when their registration window will be posted. Many students confuse this with when they can register for courses. The date and time posted on your Student Center is actually when you are able to register for courses.
Prior to your registration window being posted on your Student Center, you can find a date range of when you will register for courses on the Registrar's website at https://registrar.osu.edu/registration/. Click on current term under "Important Dates". If you scroll down, you'll find a window that lists when students will schedule based on rank.