According to Billboard, the record industry is working on creating a global standard for release day. The day suggested would make the standard release day for all releases be on Friday. (In the US and Canada, it is Tuesday).
The reason for the change is to combat piracy. Right now, the "earliest" release day is Friday, which is used in Australia. Between Australia's Friday releases, and North America's subsequent Tuesday releases, digital piracy in unavailable albums spikes.
Some sources report that the global Friday release date is already set into motion and may take effect in July 2015. Other sources state that the shift is just in consideration. You can read the whole report here.