Before 1976 the week began in Germany on Sunday, and this Jewish and Christian tradition still exists today in the USA, Israel, Japan and China.

The first day of the week is determined by the Samsung calendar of the standard location, but we can also define the beginning of the week as Saturday, Sunday or Monday.

Android 10 (One UI 2.0)
Step 1:  Open the  Calendar -App
Step 2:  Open the  menu
Step 3:  Open the  Settings
Step 4:  Tap on  First day of the week
Step 5:  Choose between  Local default ,  Saturday, Sunday  and  Monday
  1. Open the Calendar-App
  2. Open the menu
  3. Open the Settings
  4. Tap on First day of the week
  5. Choose between Local default, Saturday, Sunday and Monday

Samsung Instructions