Oppo
Switch Between 12- and 24-Hour Time Format auf Oppo
Oppo phones running ColorOS set the clock to 24-hour format by default, regardless of the region you selected during setup. This is a system-wide clock setting, not something tied to your keyboard language or SIM region, which is why changing those does not affect the time display.
The setting lives under Settings ➔ Additional settings ➔ Date & time ➔ Enable or disable 24-hour format. Toggling this option switches the format instantly across the status bar, lock screen clock, and most system apps like Clock and Calendar.
Some third-party apps and widgets read their own time format setting instead of the system one. If a specific app still shows the wrong format after you change the system setting, check that app's own display options before assuming the phone setting failed.
Automatic date and time can also override manual changes if your carrier or network pushes a different format. If the toggle keeps resetting after a restart, disable automatic time first, then set the format manually.