I work 10 to 6 but I’ve been lucky enough to continue working from home (for now at least).
Regardless of the time of day, what kills me more than anything is total hours worked. Like others have said, it’s not a fully productive 8 hours.
Anything past 6 hours and my brain mentally starts shutting down. During high stress or high productivity days that can be shortened to 4 or 5 hours of actual productivity and then I slow down