Lol this is maybe so unnecessary but me and my husband think different on this topic so we always end up confusing each other. It makes me curious to know how others look at it. I'll try to explain it in an easy way.

You had lunch at a nice place on thursday. It's passed midnight (so it's friday now) and you still haven't slept. You have an appointment at the dentist on friday. Technically thursday has become yesterday and friday has become today. But do you refer to things in that way? Or would you still refer to things based on "feel" I guess?

For example. Would you say

1. Lunch *yesterday* was nice. I need to go to bed because *today* I need to be on time for my dentist appointment.

Or

2. Lunch *today* was nice. I need to go to bed because *tomorrow* I need to be on time for my dentist appointment.