I did have the problem that if someone uploaded a file to a CCM library within a Community, the Activity Stream entries for "Recent Updates" and the users homepage did not appear immediately but appeared only the next day at 12:00 am.
The reason for that was, that someone had created schedules for the CCM Sweep Subsystem. One schedule for every day, starting at 12:00 am.
You can find that setting in the ACCE under "ICDomain -> Sweep Subsystem: Schedule":
After I deleted all schedules (on the screenshot you just see three entries, you need to scroll down to see all schedules that are defined!) and saved the configuration in the ACCE, all activity stream entries for that day were published immediately and now the entries appear immediately after a user uploads a files ...