How to search in Google Calendar
Using the search function in Google Calendar is similar to searching on Google.com. To search for events on your calendars, use the search box at the top of the page. For example, if you're looking for an event that contains the word 'swimming,' type [ swimming ] in the search field and click Search My Calendars. The search results will only contain events from calendars that are selected for viewing in your calendar list. (Calendars that are selected for viewing are highlighted by a colored bar. To select a calendar, simply click on the title in the calendar list.)
You can expand or refine your searches using Google Calendar search options. Just click Show Search Options (at the top of the page, next to the 'Search My Calendars' box), complete the appropriate fields, and press Enter.
Reference How to search in Google calendar