The Samsung calendar uses information such as appointments, tasks, birthdays etc. from your own phone memory or from accounts such as those from Samsung and Google, and you can also add an Exchange account.

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  Add new account
Step 5:  Choose desired  Account
  1. Open the Calendar-App
  2. Open the menu
  3. Open the Settings
  4. Tap on Add new account
  5. Choose desired Account

Samsung Instructions