I'm glad to be corrected. As the Cold Case reporter for the Denver Post told me, "put something you're not sure of out in the internet and somebody will tell you the answer."
I thought the first time I encountered a Day-Niter was in the CN/VIA transition, but in going through stuff that I'm trying to weed out I found an itinerary from December 1974 that probably was a Day-Niter from Vancouver, BC to Edmonton. The timetable for that trip also shows Train 10 from Prince Rupert extended to Saskatoon to handle Christmas traffic, scheduled thirty minutes ahead of us between Jasper and Edmonton.
I do remember that the car was so quiet that during an over length stop in North Kamloops everyone could hear an elderly couple arguing from the other end of the car.