<C:calendar-query xmlns:D="DAV:" xmlns:C="urn:ietf:params:xml:ns:caldav">
    <D:prop>
        <C:calendar-data/>
        <D:getetag/>
    </D:prop>
    <C:filter>
        <C:comp-filter name="VCALENDAR">
            <C:comp-filter name="VEVENT">
                <% if(end){ %>
                   <C:time-range start="<%= start %>" end="<%= end %>"></C:time-range>
                 <% } else{ %>
                   <C:time-range start="<%= start %>"></C:time-range>
                <% } %>
            </C:comp-filter>
        </C:comp-filter>
    </C:filter>
</C:calendar-query>