By default, user information is not captured and stored during the creation process of records in AtoM. However, in 2.6, some basic audit log functionality was added for archival descriptions. When enabled, this will track creation and modification events per user, and per description. The details of the changes made during modifications are not captured, but it does include date, record, and user information for each change.
This setting must be enabled for the information to be collected - meaning that enabling it does not automatically make previous activity available for review. Only additions and changes made after the setting is enabled will be captured. See:
There are further links from that section of the settings documentation that will show you how to view all changes associated with a particular description, or a particular user.
When enabled, this functionality also allows you to apply usernames as a filter in the Description updates
module (i.e. "Newest additions") - and the Description updates page already includes a date range search. Unfortunately, the results of a search here do not include the username, so you'd still need to go to each description to see its modification history, or else go to each user profile and view their modification history that way. We don't currently have a global report that covers exactly what you want.
That said, once the description change logging (i.e. the audit log functionality) has been enabled via settings and has begun collecting data, I suspect it would be possible to use SQL to output the type of information you'd like to see. It will require several joins across tables however - I don't have such a query prepared to share, but I can point you to some resources that might help you construct one yourself:
Adding support for something like a CSV or PDF report that can be generated via the user interface will require analysis and development to implement.