If you do not have to use multiview calendars, then you can set autopostback to false for the three calendar instances and the following works nicely to navigate by month/year in each direction. (see code that follows).
use multiview calendars, then you will have to set triplets containing the focused date for each calendar client side, save the values in hidden field(s), and pass this to the code behind and reset the calendars on Page_Load. And, in order to accomplish this, you would need to determine, server-side, which button was clicked. You can refer to this link for more information how this can be accomplished:
<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="Default.aspx.cs" Inherits="Default" %>
<head runat="server">
<title></title>
<telerik:RadStyleSheetManager id="RadStyleSheetManager1" runat="server" />
</head>
<body>
<form id="form1" runat="server">
<telerik:RadScriptManager ID="RadScriptManager1" runat="server">
<Scripts>
<%--Needed for JavaScript IntelliSense in VS2010--%>
<%--For VS2008 replace RadScriptManager with ScriptManager--%>
<asp:ScriptReference Assembly="Telerik.Web.UI" Name="Telerik.Web.UI.Common.Core.js" />
<asp:ScriptReference Assembly="Telerik.Web.UI" Name="Telerik.Web.UI.Common.jQuery.js" />
<asp:ScriptReference Assembly="Telerik.Web.UI" Name="Telerik.Web.UI.Common.jQueryInclude.js" />
</Scripts>
</telerik:RadScriptManager>
<telerik:RadCodeBlock ID="RadCodeBlock1" runat="server">
<script type="text/javascript">
function NavigatePrevYear() {
var calendar = $find("<%=RadCalendar1.ClientID%>");
var triplet = [calendar.FocusedDate[0] - 1, calendar.FocusedDate[1], calendar.FocusedDate[2]];
calendar.navigateToDate(triplet);
var calendar2 = $find("<%=RadCalendar2.ClientID%>");
var triplet = [calendar2.FocusedDate[0] - 1, calendar2.FocusedDate[1], calendar2.FocusedDate[2]];
calendar2.navigateToDate(triplet);
var calendar3 = $find("<%=RadCalendar3.ClientID%>");
var triplet = [calendar3.FocusedDate[0] - 1, calendar3.FocusedDate[1], calendar3.FocusedDate[2]];
calendar3.navigateToDate(triplet);
}
function NavigatePrevMonth() {
var calendar = $find("<%=RadCalendar1.ClientID%>");
var triplet = [calendar.FocusedDate[0], calendar.FocusedDate[1] - 1, calendar.FocusedDate[2]];
calendar.navigateToDate(triplet);
var calendar2 = $find("<%=RadCalendar2.ClientID%>");
var triplet = [calendar2.FocusedDate[0], calendar2.FocusedDate[1] - 1, calendar2.FocusedDate[2]];
calendar2.navigateToDate(triplet);
var calendar3 = $find("<%=RadCalendar3.ClientID%>");
var triplet = [calendar3.FocusedDate[0], calendar3.FocusedDate[1] - 1, calendar3.FocusedDate[2]];
calendar3.navigateToDate(triplet);
}
function NavigateNextMonth() {
var calendar = $find("<%=RadCalendar1.ClientID%>");
var triplet = [calendar.FocusedDate[0], calendar.FocusedDate[1] + 1, calendar.FocusedDate[2]];
calendar.navigateToDate(triplet);
var calendar2 = $find("<%=RadCalendar2.ClientID%>");
var triplet = [calendar2.FocusedDate[0], calendar2.FocusedDate[1] + 1, calendar2.FocusedDate[2]];
calendar2.navigateToDate(triplet);
var calendar3 = $find("<%=RadCalendar3.ClientID%>");
var triplet = [calendar3.FocusedDate[0], calendar3.FocusedDate[1] + 1, calendar3.FocusedDate[2]];
calendar3.navigateToDate(triplet);
}
function NavigateNextYear() {
var calendar = $find("<%=RadCalendar1.ClientID%>");
var triplet = [calendar.FocusedDate[0] + 1, calendar.FocusedDate[1], calendar.FocusedDate[2]];
calendar.navigateToDate(triplet);
var calendar2 = $find("<%=RadCalendar2.ClientID%>");
var triplet = [calendar2.FocusedDate[0] + 1, calendar2.FocusedDate[1], calendar2.FocusedDate[2]];
calendar2.navigateToDate(triplet);
var calendar3 = $find("<%=RadCalendar3.ClientID%>");
var triplet = [calendar3.FocusedDate[0] + 1, calendar3.FocusedDate[1], calendar3.FocusedDate[2]];
calendar3.navigateToDate(triplet);
}
</script>
</telerik:RadCodeBlock>
<div>
<table>
<tr>
<td>
<telerik:RadButton ID="RadButton1" runat="server" AutoPostBack="false" Text="<<" OnClientClicked="NavigatePrevYear" >
</telerik:RadButton>
<telerik:RadButton ID="RadButton2" runat="server" AutoPostBack="false" OnClientClicked="NavigatePrevMonth" Text="<" >
</telerik:RadButton>
<telerik:RadButton ID="RadButton3" runat="server" AutoPostBack="false" OnClientClicked="NavigateNextMonth" Text=">" >
</telerik:RadButton>
<telerik:RadButton ID="RadButton4" runat="server" AutoPostBack="false" Text=">>" OnClientClicked="NavigateNextYear" >
</telerik:RadButton>
</td>
</tr>
<tr>
<td>
<telerik:RadCalendar ID="RadCalendar1" runat="server" AutoPostBack="false" ShowRowHeaders="false" FocusedDate="1/1/2012 12:00:00 AM" >
<SpecialDays>
<telerik:RadCalendarDay Repeatable="Today" Date="" ItemStyle-CssClass="rcToday">
<ItemStyle CssClass="rcToday"></ItemStyle>
</telerik:RadCalendarDay>
</SpecialDays>
</telerik:RadCalendar>
</td>
<td>
<telerik:RadCalendar ID="RadCalendar2" runat="server" AutoPostBack="false" ShowRowHeaders="false" FocusedDate="1/1/2013 12:00:00 AM" >
<SpecialDays>
<telerik:RadCalendarDay Repeatable="Today" Date="" ItemStyle-CssClass="rcToday" />
</SpecialDays>
</telerik:RadCalendar>
</td>
<td>
<telerik:RadCalendar ID="RadCalendar3" runat="server" AutoPostBack="false" ShowRowHeaders="false" FocusedDate="1/1/2014 12:00:00 AM" >
<SpecialDays>
<telerik:RadCalendarDay Repeatable="Today" Date="" ItemStyle-CssClass="rcToday" />
</SpecialDays>
</telerik:RadCalendar>
</td>
</tr>
</table>
</div>
</form>
</body>
</html>