iPhoto mess

I was trying to assemble pictures into albums in iPhoto, by selecting several and draging the group of pictures into the albums. I dont know what happened, but now in the "Events" and "Photos" libraries, all the photos are mixed up. I have them sorted by date, and some are in the appropriate group of pictures for a particular date, with one date for that group, but some groups have pictures grouped together with a HUGE date range.

Is there any way that I can get them back in the correct groupings and in chronological order, or am I going to have to painstakingly do it one picture at a time? I have gone to "VIEW>SORT>SORT BY DATE", but that does nothing.

Thank you.