[Plugin: Edit Flow] November days numbered wrong

I have this same problem with two Nov 2nd so that every date thereafter is on the wrong day of the week. It is misbehaving on only 1 of the 12 sites where I use this plugin. I’d love a solution!

I’ve tried uninstalling and reinstalling, and uninstalling all other plugins one at a time. All the sites are custom WP themes, self hosted, and all built by the same people. We’ve used Edit Flow successfully for over a year and we keep everything updated.