Disable a date in datepicker

http://www.telerik.com/forums/disable-specific-date-in-datetimepicker

http://stackoverflow.com/questions/28064764/disable-unwanted-dates-in-date-picker-in-c-sharp-window-application

http://stackoverflow.com/questions/2361691/how-do-i-disable-some-dates-on-a-datetimepicker-control

http://www.aspforums.net/Threads/152677/Disable-some-dates-in-DateTimePicker-control-in-Windows-Forms-WinForms-application-using-C-and-VBNet/

http://stackoverflow.com/questions/27319417/disable-some-dates-in-datetimepicker-winform-c-sharp

Refer this Hope it helps you