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You are supposed to do anything and everything to/with your photos from within the app itself. You don't need to worry about what is in the library in finder. iPhoto organizes things so that it can do the work for you. Just work from the app and forget about what the library says. If you change things there, you will render iPhoto unable to function for you.
 
it "should" work?... famous last words.

It makes complete sense that photos exported via iPhoto would maintain their origination dates, but unfortunately that is not the case. I have version 8.1.2, and all exported photos have their data (created, modified, and opened dates) wiped out and replaced with the date and time of export. Does anyone have an intelligent (i.e more than "it should work") work around for this pathetic flaw in the program? In fact, before this application sealed the library I was able to export photos and maintain the meta data.
 
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