The answer is here:

https://www.odoo.com/forum/help-1/question/how-to-get-reminder-for-scheduled-phone-call-9871

Pay attentions to this app - https://apps.odoo.com/apps/modules/9.0/joint_calendar/. It adds advanced features to a standard Odoo calendar

hi,

reminder in Mail is not working.

if you want to get reminder every day.then follow the example.

1.you have to create one event like start date 08/20/2015 12:37:00 and end date 12:38:00. then goto option and Checked on Recurrent select Repeat every 1 and day until end date is 12/20/2015.

2. Now Set Automated action with Object EVENT. Trigger Date is Start DateTime and Delay After Trigger Date -2 Minutes.

3. Create Server Action with Object EVENT. Action To Do is Send Email. Create Email Template.

How it's work. Every Day Before the starting Event 08/21/2015 12:37:00(every day till recurrent last date). Email is Sending to Attendee.

I hope this will Work Perfect.I am Satisfied with this Action and it's work Perfect.

if anyone want to screen. Inform me.