alt Hacker NewsWearing a Casio as I type this. The "24hr" button switches 12/24 modes on the "watch" mode, when using stopwatch it starts the watch, and when using alarms it turns the alarm on/off.
It has pretty critical functionality for those, I think the way its labeled on the watch face just makes it sound a little odd.
Now that I think I can't very fast come up with any feature I would want to have on third button in clock display mode. UI is 3 buttons, light, mode and one mode dependant. So I can't think what you would use it for in clock mode. So better have it work, but do something inconsequential...