When I moved to Ireland, I noticed they used the 24-hour system for their clocks, i.e. 15:00 for 3PM or 22:00 for 10PM. This was helpful because I had changed my sleep schedule dramatically from late in the afternoon to about midnight. I did this to be able to dominate the TV for video games without interruption and to accommodate the time different to chat with people online. With most people if someone said, "I'm eating dinner at seven," you'd understand it was nighttime. That no longer applied to me, who often ate at 5AM. To avoid confusion I started to write with the 24-hour system as well, a habit that continues to this day.

Unfortunately my brain really started to think along those lines, to the point it's starting to fuck me up. For example my clock has a 12-hour system, with a little dot on the side stating whether it's morning or evening. A little while ago I had to wake up at 6:00 and set it accordingly. Unfortunately I forgot a few days prior I set it to wake me up from my nap at 17:00, meaning when I adjusted the alarm time for one hour I had actually set it to 18:00. I can't tell you how often this happens. I've nearly been late to gatherings, weddings, and flights. This wasn't a problem before — I always paid attention to that little dot — but now I see 6:00 and just automatically think it means morning.