Skybox team, the date currently used for sorting purpose is based on the date & time on which the thumbnail of the movie is processed through initially adding into the list of movies in PC client.
However, once the PC client is crashed or being updated into different version, the date is lost and upon re-processing, the date being used will be based on the date & time on the whole batch of movies being processed which renders the date become meaningless.
Unless the date will not be lost for whatever reason, I strongly suggest that such method should not be used and it's not workable in long run. Instead, as per Toran's suggestion, I also agree that the date should be based on the date on which the movie created as shown in its property:
