One morning, a few weeks back, I made eye contact with someone who was obviously having a rough morning. I knew I shouldn't engage but I also didn't want to ignore them, so I gave a quick good morning. They promptly responded, "fuck your morning."
Reminds me of my Lithuanian colleague, who would walk into the office and not say anything. If you greeted her, she'd cast you a wary look like what's so special about this morning to make it "good" mothafucka
I like to stick with a simple "hello" so I don't have to keep track of time (e.g. during meetings across timezones or even when I'm so scatterbrained that day that I lose track of local time) and it's also less presumptuous.
People have accepted that 'morning' is my standard greeting regardless of the time of day. It's even become a thing everyone says within my close friend group.
"What do you mean?" he said. "Do you wish me a good morning, or mean that it is a good morning whether I want it or not; or that you feel good this morning; or that it is a morning to be good on?"