Thanks for sending the photo, @scincus, I was able to replicate and I’m pretty sure it’s related to the daylight savings time change. If I change the location to a state that doesn’t observe DST (like Arizona or Hawaii), the correct date is shown.
I’ve made a github issue here: https://github.com/inaturalist/inaturalist/issues/3692
Time zones have been automatically determined by the observation’s location for about a year now.