Google Calendar is a great instrument, but it has one feature: if for some reason you are not checking calendar notification for a while, it disappears after about an hour.
This app fixes it for you!
How it works: this app listens for notifications posted by Google Calendar, and replaces them with its own similar looking notifications that will remain in the notification area even after reboot, until you dismiss them manually!
Apart from slightly different look, behavior of notification is exactly the same: on clicking it you'll get Google Calendar opened with Event View activity.