Search that would list System Notes of an Account in a given period

 1.  Navigate to Reports> New Search> Accounts> click on Create Saved Search button
 2. Rename Search Title
 3. On the Criteria tab > Standard sub tab
      >> Internal Id  (of the Account)
      >> System Notes Fields... then select desired date
 4. On the Results tab> Columns sub tab add the following fields:
      >> Name 
      >> System Notes Fields... the click Add Multiple and select all.
 5. Save and Run

Note: System Notes in Chart of Accounts was introduced on version 2011.2 thus it will yield prospective changes only.