Google (Anurag Acharya and Darcy Darpa) has contacted DuraSpace about a common indexing issue affecting all DSpace sites.
When Google & Google Scholar index DSpace content (from a variety of institutions), the "dc.date.issued" value is incorrect the majority of the time. The reason is that, if unspecified, DSpace sets this issued date to the date of accession (i.e. date that it was submitted to DSpace), see:
Google says this causes their crawlers (for both Google & Google Scholar) to assume that the date of accession is actually the formal publication date.
Rather than defaulting the 'dc.date.issued' to the accession date, Google recommends we leave it blank. DSpace is already tracking the accession date separately (in 'dc.date.accessioned'), so it seems odd to set 'dc.date.issued' to the same value by default.
Google will be sending along some examples of this. They said they have seen repositories, where 30-50% of their items all have the same "dc.date.issued", as those items were all imported on the same date.
This seems like a very reasonable recommendation to me as well. I'm not sure we should be setting 'dc.date.issued' by default, as it really is meant to be the date of formal publication, and not the date that something is made available on the web.
This also seems like a small fix (remove a few lines from InstallItem).