Microsoft will be rolling out calendar search for Office 365 users over the next several months.
Calendar Search allows you to search your own calendars or Group calendars for events in the past, present, and future. You can also search for people’s calendars and overlay their calendars on top of yours for quick comparison.
To search your calendar using a keyword or phrase, while your calendar is selected you simply type a keyword in the search box and click or tap enter (or the search icon).
The Outlook Web App shows results based on the term you typed, whether that term appears in the body, title, or location of the event, in the name of an attendee/organizer, or even in the name of a category applied to an event. Calendar Search groups results by month and orders them in descending order by date.
Microsoft has provided a FAQ:
Q: When will Calendar Search be available?
Calendar Search will roll out to Office 365 customers over the next several months.
Q: Does the Outlook desktop client show people’s calendars I have searched for?
Outlook desktop client only pins to the calendar list those people you choose to favorite.
Q: Can I search multiple calendars at once?
No, it is not currently possible to search multiple calendars at once.
Q: Can I search other people’s calendars?
Calendar Search is currently limited to your primary calendar, your secondary calendar, and Group calendars.
Source: Office Blog