I start work at 9:00 most days, as do most of my coworkers. Earlier this month, at 6:54 one morning, I was emailed an invitation for a meeting at 8:00. I was later asked why I didn't attend.

I'm not sure if I'd say I was angry, but I definitely wasn't happy about it. That's not just an email, to be fair, but still feels like it counts.

They can just look at the time they received it? I think the overwhelming majority of emails are sent instantly, not delayed, so you don't really need to look at the sent time.