Way to auto-group existing photos into events? I migrated from primarily a PC desktop to a Macbook Pro, and with that, brought along 10+ years of digital photos. On my PC, I had each 'event' grouped into sub-folder by date, so that worked out well importing into iPhoto-- but I also had iCloud setup on my PC, and it was syncing my Photostream (into just one big folder, with 1800+ photos). Bringing this over to iPhoto I now have "one event" named Photostream that has all these photos. Is there any way to have iPhoto just automatically group these by date into new events?
In iPhoto > Preferences > General there is an option "Autosplit into Events" that you can set. 

If all you are seeing is the one Photostream event, I'd guess that it isn't finished importing and it will split the events when it is done.

I don't have a photostream event in my events in iPhoto, I just have an iCloud tab that is on the same level in the sidebar as Events.