Why does my S. Galaxy s9 keep going to military time

[Android Central Question]

I can switch my time back to the regular 12-hour time but when I turn the screen on or off it returns back to military time with all these steps that takes to get to military time I don't understand why I keep having two go through all the steps to return it to regular time when all it takes is a screen to timeout and I turn it back on and it goes back to military time