I am afraid this is not supported at present by Kendo UI Calendar. Actually this idea has been already submitted as a feature request, so if you wish you may case a vote, leave a comment or monitor the community's interest in it here. The more votes the suggestion collects, the higher priority will have.
Meanwhile as a possible workaround I can suggest you to attach a handler to the Calendar's change event and prevent it if the selected date is out of some range. Also you should apply custom CSS in order to get "disabled" outcome for the aforementioned dates.
the Telerik team
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