The Search option makes it easier for you to find any event in your Calendar using keyword(s).
1. When in Mail, click on Calendar and locate the Search field under the top ribbon.
2. Type a keyword(s) related to the event you are searching for and press Enter (this is the basic way to search for an event in Calendar).
3. Search will extract all the events containing the typed keyword(s) anywhere in their content.
4. Double-click on a given result to review it.
For a more advanced search, there are predetermined keyword(s) and phrases you can use.
You can find the complete list of quires here.