kendo datepicker change event doesn't refresh the month view

kendo datepicker change event doesn't refresh the month view

I have a kendo date picker defined as follows:
<input id="datePicker" data-format="dd.MM.yyyy" data-month='{ "content":
"&lt;span class=\"#= dateRange.hasReport(data.date) ? \"boldDate\" :
\"normalDate\" #\"&gt;#=data.value #&lt;/span&gt;" }'
data-role="datepicker" data-bind="value: new Date(), events: {change:
dateChanged}" style="width:150px;" />
In the month template, I bold some dates depending on whether there is a
report or not for that date by a call to the method
dateRange.hasReport(data.date)
Now, there is an external event which causes the daterange to change. I
want to now refresh the calender view so that the dateRange.hasReport is
called for all dates again.
I am unable to find a way to do this.
Any ideas?