West coast report:
- interviews are mostly on weekdays because faculty/staff don't want to work weekends
- this is a weird holiday year with Christmas & New Years falling on weekends
- I wouldn't be surprised if there are no interviews the week before nor after Christmas
- regardless I wouldn't worry about "losing" interviews for a holiday week
- every program is different
- when you get offered an interview, you usually get offered a number of days to choose from
- InterviewBroker is terrific
Also, before you schedule travel, figure out how to be at the social event. Responsible programs will commit to weekly day/time/location for the social event long before you get invited. Go & close the deal.
Good luck!