You will have two interviews; one faculty interview and one student interview. The faculty interview can occur any time during the day, depending on the faculty's availability. I had mine at 2pm, while others had theirs at 9am, for instance. The tone depends on the interviewer, but in general, it is pretty laid back. They will have a list of standard questions prepared, but may or may not adhere to the list. The faculty interview is open file.
The student interview takes place in the afternoon, either at 2pm or 3pm. The student has access to your activities and your personal statement. They also have questions prepared for you. Something to keep in mind is that the student interview is given equal weight as the faculty interview, so make sure to shine 🙂
Other than the interviews, the day is pretty relaxed. There's a bit of downtime, and you'll get a chance to wander the building and mingle with other interviewees.
You will hear from some members of the admissions committee as well as from the financial aid folks. You'll have lunch with a few students, and then go on a student led tour of the buildings.
The day should end at around 4 at latest, earlier if your faculty interview is in the morning.
That's about all I can remember.
Good luck! 🙂