There is a new functionality in your CRM since version 18.104.22.168 that allows you to create a report about accounts which includes a special filter. That filter enables you to select a date specifying the last desired activity of an account.
The report will list every account that has not been contacted since the specified date or not contacted at all.
To create such a report you have to select Accounts as the primary module. You will find a new entry in the filter tab named “last Activity” (very last of filter options belonging to Accounts). Select “less than” and the desired date and you are ready to go.
Should you add Calendar as a secondary module you will be able to get information about the latest activity done, should there be one.