As of June 27 2015 Google Calendar will no longer sends an SMS (event) notification before an event. This feature is still available for paying Google users (Google apps for work). If you still want to send SMS notifications to yourself (or others) you can use Un4gettable which integrates seamlessly in the Google Calendar UI. It's free if you send less than 10 reminders each month. Un4gettable is made for appointment reminders, but it is suitable also for this job.