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<concept id="GUID-579EF7F5-EA93-40D1-917F-95B966D1BAB2" xml:lang="en"><title>Working
with Skipped Calendar Alarms - Overview</title><shortdesc>This topic introduces a set of tutorials on working with Calendar
alarms that have been skipped because of environment changes. </shortdesc><prolog><metadata><keywords/></metadata></prolog><conbody>
<section id="GUID-D75C3FEA-664E-4526-872E-BFC73BAF6F64">       <title>Required background</title>       <p>Familiarity with:</p><ul>
<li><p><xref href="GUID-00631ED2-1B7F-5FC4-9E81-4B6DF7946631.dita">Calendar</xref> and <xref href="GUID-114D4F3F-9358-5B50-94DC-45CCBA783DF4.dita">Alarm Server</xref> functionality.</p></li>
<li><p>Skipped Alarms property keys in the <xref href="GUID-8FAC10FB-BCD1-3373-9440-EF2EED70A861.dita"><apiname>TASShdAlarm</apiname></xref> class.</p></li>
<li><p><xref href="GUID-C705B0D5-055A-5DAA-9C6E-2FC3519FA50C.dita">Publish and
Subscribe</xref>. </p></li>
</ul>     </section>
<section id="GUID-7A034BBB-52F3-4AFA-B40E-26B563491255">       <title>Introduction</title>       <p> 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. </p><p> An
environment change is one of the following: </p><ul>
<li><p>A system time change. </p></li>
<li><p>A time zone change. This is similar to a Coordinated Universal Time
(UTC) change. </p></li>
<li><p>A Daylight Savings Time (DST) observation period beginning or ending.
(Similar to a UTC change.) </p></li>
</ul><p> Each Calendar instance has a <xref href="GUID-725D11A2-8805-3466-98DB-EF5CDEAF2801.dita"><apiname>CCalEntry</apiname></xref>. When the <codeph>CCalEntry</codeph> has
an associated <xref href="GUID-211D3640-9862-3F78-98FC-9793578117A9.dita"><apiname>CCalAlarm</apiname></xref>  it becomes an alarmed Calendar
instance. </p><p> When an environment change occurs the Alarm Server can respond
to the skipped alarms in one of two ways: </p><p> <i>Queue an alarm which
then expires</i></p><p>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. </p><p><i>Notify a subscriber
about the skipped alarm</i></p><p> 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. </p><p>To learn how a subscriber can
be notified of skipped Calendar alarms and respond to them see the tasks below.</p> 
   </section>
<section id="GUID-95A0061F-EFAC-44FB-93C1-7D6BDB6C8A25">       <title>Tasks</title><ul>
<li><p><xref href="GUID-CA933F35-7508-5C98-9DB6-2492803A2183.dita">Reading a Skipped
Alarm Property</xref></p></li>
<li><p><xref href="GUID-BF8C56B7-1F39-502F-B9CA-81E9272CC945.dita">Reading a Skipped
Alarm Instances Property</xref></p></li>
<li><p><xref href="GUID-E3981A14-DD2C-5582-A250-C2AD358729FD.dita">Retrieving Skipped
Alarmed Calendar Instances</xref></p></li>
</ul>           </section>
</conbody></concept>