For the time being the property can be set through the kendoWidget:
Available options can be found here - http://docs.telerik.com/kendo-ui/api/dataviz/chart#configuration-categoryAxis.weekStartDay
		<script>
			function pageLoad() {
				var kendoWidget = $find("<%=RadHtmlChart1.ClientID%>")._chartObject;
				kendoWidget.options.categoryAxis.weekStartDay = 1;
				kendoWidget.redraw();
			}
		</script>
		<telerik:RadHtmlChart runat="server" ID="RadHtmlChart1" Width="600px" Height="400px">
			<PlotArea>
				<Series>
					<telerik:ColumnSeries Name="Product 1" DataFieldY="SellQuantity">
					</telerik:ColumnSeries>
				</Series>
				<XAxis DataLabelsField="SellDate">
					<LabelsAppearance DataFormatString="yyyy/MM/dd"></LabelsAppearance>
				</XAxis>
			</PlotArea>
		</telerik:RadHtmlChart>