I recently finally upgraded to Windows 10. Like all my upgrades, I didn't actually upgrade, I used the license to do a clean install. It took me a couple weeks to notice, but I am now noticing that the time is being displayed on the lock screen and in the alarms app in the 24h format, But the time is in the regular 12h format on the clock on the taskbar, at the bottom right of the screen. Are there two separate time and date settings in Windows 10???
OK I literally just stumbled across the answer right after posting this. I found that the date and time on the lock screen and the alarms app is set to what is known as the "long time" while the conventional clock in the task bar is set to the "short time". Apparently Windows default settings are to use 24H as long time and 12h as short time. Kind of odd to mix those opposing formats if you ask me. You can change this either from the traditional Region settings in Control Panel, or from the new Settings "app" which I absolutely loath.
EDIT: That's interesting, the icon for the "Programs" entry on the root of my Control Panel menu has changed to a big solid black box. Oh wait, now it looks normal again. What the heck is happening to my computer???