This helpful tool will send students reminders about upcoming events on the Moodle calendar. The addon was created by Isuru Madushanka Weerarathna as part of the 2012 Google Summer of Code and can be configured similarly to Google Calendar’s event reminders (though these event reminders are globally configured rather than on an event by event basis and have only 3 options for when reminders are set: 1, 3 and 7 days prior).
Download the plugin: https://moodle.org/plugins/view.php?plugin=local_reminders
Read the documentation: http://docs.moodle.org/23/en/admin/setting/local_reminders