By default, the start of the week is set according to the region set on the Xiaomi smartphone, but this can be changed if desired, allowing us to choose whether the week starts on a Saturday, Sunday or Monday, which will also adjust the calendar view accordingly.

Android 10 (MIUI 12.0)
Step 1:  Open the  Calendar app
Step 2:  Open the  menu
Step 3:  Open the  Settings
Step 4:  Tap on  Start of the week
Step 5:  Choose  Region default ,  Saturday ,  Sunday  or  Monday
  1. Open the Calendar app
  2. Open the menu
  3. Open the Settings
  4. Tap on Start of the week
  5. Choose Region default, Saturday, Sunday or Monday

Xiaomi Instructions