Dated
exchange rates allow you to map a currency conversion rateto a specific date range. Dated exchange rates are used for opportunities, opportunity products, opportunity product schedules, campaign opportunity fields, and reports related to these objects and fields

The "Contact to Multiple Accounts" feature in Salesforce allows a single contact to be associated with multiple accounts without the need to duplicate the contact record. This is particularly useful for tracking relationships where a contact has roles in multiple organizations, such as in this scenario where the contact is associated with both a business account and a nonprofit. Enabling this feature provides an efficient solution to manage complex relationships.
Reference:
Contacts to Multiple Accounts
Enable Contacts to Multiple Accounts