Dude, Sometimes at work I ask people when they arrived in the area to make conversation and if they answer a specific day like Thursday instead of saying something like 3 days ago I just smile and say cool. I literally never know what day it is.
I started a new job yesterday and today my manager asked me to write my hours on the schedule since I couldn't punch in yet. I spent like 5 minutes trying to figure out how to figure out what day it was without having to ask. The worst part was that next weeks schedule was up and I didn't even know what week it was.
You're only off by one day, you're doing pretty good in my opinion.