Appointment: Not be able to get appointment using "SearchRequest" soap API

[hiteshk25]

I am sending following soap request to fetch the appointments.
//*****************************Soap Request***************************
<soap:Envelope xmlns:soap="http://www.w3.org/2003/05/soap-envelope">
<soap:Header>
<context xmlns="urn:zimbra">
<authToken>0_323dca859239d8039e827d94641e3c8d5dadd 79e_69643d33363a31313161363435372d633464382d343235 332d626330632d3132633864373635373966613b6578703d31 333a313230373831393639373235343b747970653d363a7a69 6d6272613b6d61696c686f73743d31323a3132372e302e312e 313a38303b</authToken>
<account by="name">hitesh2@capricorni.gs-lab.com</account>
</context>
</soap:Header>
<soap:Body>
<SearchRequest limit="500" sortBy="none" types="appointment" calExpandInstStart="1207430897464" calExpandInstEnd="1207862897464" xmlns="urn:zimbraMail"/>
</soap:Body>
</soap:Envelope>
//************************************************** ******************

And getting following response

//************************************************** ****************
<soap:Envelope xmlns:soap="http://www.w3.org/2003/05/soap-envelope">
<soap:Header>
<context xmlns="urn:zimbra">
<sessionId id="194">194</sessionId>
<refresh>
<version>5.0.4_GA_2101.UBUNTU6 20080321150617 20080321-1507 FOSS</version>
<mbx s="20619"/>
<tags/>
<folder id="1" rev="1" s="0" name="USER_ROOT" n="0" l="11">
<folder id="16" rev="1" s="0" name="Briefcase" n="0" l="1" view="document" rest="http://capricorni.gs-lab.com/home/hitesh2/Briefcase"/>
<folder f="#" id="10" rev="1" s="17076" name="Calendar" n="4" l="1" view="appointment" rest="http://capricorni.gs-lab.com/home/hitesh2/Calendar"/>
<folder id="14" rev="1" s="0" name="Chats" n="0" l="1" view="message"/>
<folder id="7" rev="1" s="0" name="Contacts" n="0" l="1" view="contact" rest="http://capricorni.gs-lab.com/home/hitesh2/Contacts"/>
<folder id="6" rev="1" s="0" name="Drafts" n="0" l="1" view="message"/>
<folder id="13" rev="1" s="0" name="Emailed Contacts" n="2" l="1" view="contact" rest="http://capricorni.gs-lab.com/home/hitesh2/Emailed%20Contacts"/>
<folder id="2" rev="1" s="1503" name="Inbox" n="1" l="1" view="message"/>
<folder id="4" rev="1" s="0" name="Junk" n="0" l="1" view="message"/>
<folder id="12" rev="1" s="0" name="Notebook" n="0" l="1" view="wiki" rest="http://capricorni.gs-lab.com/home/hitesh2/Notebook"/>
<folder id="5" rev="1" s="2038" name="Sent" n="5" l="1" view="message"/>
<folder f="#" id="15" rev="1" s="0" name="Tasks" n="0" l="1" view="task" rest="http://capricorni.gs-lab.com/home/hitesh2/Tasks"/>
<folder id="3" rev="1" s="0" name="Trash" n="0" l="1"/>
</folder>
</refresh>
<change token="261"/>
</context>
</soap:Header>
<soap:Body>
<SearchResponse more="0" sortBy="none" offset="0" xmlns="urn:zimbraMail"/>
</soap:Body>
</soap:Envelope>

//************************************************** ****************

I can see 4 appoinments in my folder but "searchRequest" not retrieving any one.

Please let me know where I am doing mistake.

Thanks,
HItesh