As already mentioned with the date, the time is also obtained automatically from the network; to set the time manually on the Xiaomi smartphone, the automatic date and time function must be disabled.

Android 10 (MIUI 12.0)
Step 1:  Open the  Settings
Step 2:  Tap on  Additional settings
Step 3:  Tap on  Date & time
Step 4:  Disable  Use network-provided time
Step 5:  Tap on  Time
Step 6:  Set the  time  and tap  OK
  1. Open the Settings
  2. Tap on Additional settings
  3. Tap on Date & time
  4. Disable Use network-provided time
  5. Tap on Time
  6. Set the time and tap OK

Xiaomi Instructions