Hi Vishnu ,
The modification timestamp (modification_ts) from jivedw_user table is the timestamp when the user profile is modified.You can use "jivedw_activity_fact" table to find out the users active / activity happened during that time with the help of activity timestamp.
Not sure if you can exactly match that data with CMR active users, as community manager reports gives you active users on the basis of this "Users who have viewed at least one document,discussion, blog post, status update, poll, video, idea,group overview page, space overview page, or project overview page in the previous 30 days." at a given point .
Hope this helps.
SELECT DISTINCT jivedw_user.user_id,jivedw_user.username,jivedw_user.firstname,jivedw_user.lastname,jivedw_user.modification_ts
WHERE jivedw_activity_fact.user_id=jivedw_user.user_id AND (jivedw_activity_fact.activity_ts>='2015-01-01') AND (jivedw_activity_fact.activity_ts<'2015-02-01')
Give that one a shot. As Charu Gulati mentions the data lives in jivedw_activity_fact (also could use various agg tables too but I prefer activity_fact).
The trouble with using the last modified date is that if someone used it in February but not in January the last modified would show they accessed it in Feb...but does that mean they used it in January too?