The original release date can differ from the sales start date / release date. The sales start date is the date an album will be available in a given territory. 
Accuracy. Album and track release dates should be the original date when the album or track was first released, regardless of country, or whether it was released digitally versus physically. 
Note: The original release date for rerecords must be the first date the rerecord was available, and not the release date of the original recording. Additional versions of an album that are not rerecords (for example, remastered, reissued, or bonus versions) must still be given the original release date for the album and original tracks. Any previously unreleased or bonus tracks should receive the release date of when these were first made available.