[U]Tech is making a change to a Google Calendar default. Recently, Google implemented a way to prevent meeting invitations from unknown individuals automatically appearing on your calendar. On Thursday, Sept. 22, [U]Tech will change the current default of "From everyone" to "Only if the sender is known." A known sender is someone in your contacts list or with whom you’ve interacted. You will still see invitations from unknown senders in their email; however, those meetings will not appear on your calendar unless you respond to the email invitation.
To review this feature, sign into Google Calendar, click on the gear icon to open the settings, click on "Event settings" from the left side menu and click on the "Add invitations to my calendar" dropdown. You can change the setting back to "From everyone" or select "When I respond to the invitation in email" (i.e. no invitations are added automatically via email unless you respond).
For more information visit the Google Support page.