Calendar working very strangely in Tahoe

I've been on Tahoe for a few weeks now and I'm running 26.0.1. I generally look at my calendar a week at a time, Sunday → Saturday. I noticed at 1 point in Calendar today that when I clicked the right arrow to see the following week, it changed to show me Tuesday → Monday, and the next time it was Thursday → Wednesday. I let it sit for a while, and right now it's back to Sunday → Saturday. Has anyone else noticed this?