But in any case, it is not yet possible to check online intervals.
You can check if user wasn't active for longer period of time and woke up, someone archived seclog for last 5 years (
http://archive.is/https://bitcointalk.org/seclog.php), but, unfortunately, few months are missing.
I apologize if the question is off-topic (but I think this is the most appropriate thread to ask about this).
Account is not DT member, you should have created new topic in meta for this.