Now that Google started to index web pages much faster, it replaced the date when Google last indexed a page...
... with the number of minutes, hours or days since that event:
I managed to see this new format mostly for queries that use the site: operator, but it should propagated to all the queries.
I wonder if we'll ever see an option to sort the results by date or to restrict the results to a date interval (Google offers some limited options in the advanced search interface).
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