SortMyPhotostream is a tool that most Flickr users will have no use for, but one that some might find invaluable. It all depends on whether you would like your Flickr photos’ upload dates to reflect the day they were actually taken. For example, if you’re doing a Project 365 and would like each photo to show up on the day it was taken in your calendar view, then this app can help you make that happen.
All you do is give the app permission to access your Flickr account, and it automatically changes the “Uploaded on” date of each photo to the “Created on” date found in the EXIF data. If this isn’t the kind of thing you need, don’t play around with the app — changes made by it are permanent.