Google has now
added Calendar results from Gmail to search results for users who had signed up for Gmail search field trial. So if you're signed in to Gmail, and key-in a search query on Google search, you'll also see relevant calendar listings with the search results. You could also see the calendar listings by entering the search term ' what is on my calendar today' or the name of a particular event or person.
We couldn't check it as we didn't register for the field trial but according to the screenshot posted by Google, the Calendar results are displayed under the personal results, along with the option to view them in Google Calendar.
In October 2012, Google had
added Google Drive to the field trial, including Google Drive documents in search listings.
In August, Google had
announced the field test integrating its search with Gmail allowing users to search within emails for any data tied to a search request, if they were logged into their account including contacts and information from flight-related emails. In December, Google had
added support for purchases and orders, event registrations, and hotel reservations, pulling the information through Gmail when users search for 'My Orders', 'My Events' and 'My Reservations'. However, this was limited to users in the US.
It's worth noting that the field test is not available for Google Apps users. Users can
sign-up for the new expanded field trial, following which they shall receive a confirmation email from Google when their account is ready. However, the test may not be activated for everyone.
Google also offers similar feature on Google Now, a voice based information assistant and an extension of Google search which is included on Android 4.1 Jelly Bean phones. Google Now collects information based on the user's behaviour, location and email to offer information automatically.