Working with Skipped Calendar Alarms - Overview

Required background

Familiarity with:

• Calendar and Alarm Server functionality.

• Skipped Alarms property keys in the TASShdAlarm class.

• Publish and Subscribe.

Introduction

A skipped alarm is a Calendar alarm which does not expire normally because of an environment change. An environment change can put the alarm’s expiry time in the past.

An environment change is one of the following:

• A system time change.

• A time zone change. This is similar to a Coordinated Universal Time (UTC) change.

• A Daylight Savings Time (DST) observation period beginning or ending. (Similar to a UTC change.)

Each Calendar instance has a CCalEntry. When the CCalEntry has an associated CCalAlarm it becomes an alarmed Calendar instance.

When an environment change occurs the Alarm Server can respond to the skipped alarms in one of two ways:

Queue an alarm which then expires

The Alarm Server notifies Calendar that the system date/time has changed. Calendar then queues alarms that would have been skipped up to a day in the past with the Alarm Server. These alarms then expire immediately and the device user must acknowledge each of them.

Notify a subscriber about the skipped alarm

The Alarm Server uses Publish and Subscribe to notify a subscriber that one or more Calendar alarms has been skipped. The subscriber decides what action to take because Calendar does not queue skipped alarms with the Alarm Server.

To learn how a subscriber can be notified of skipped Calendar alarms and respond to them see the tasks below.

Tasks

• Reading a Skipped Alarm Property

• Reading a Skipped Alarm Instances Property

• Retrieving Skipped Alarmed Calendar Instances