It is not possible to customize the TimeSheet side calendar on the TimeSheet page. Hence, it is not possible to synchronize the TimeSheet side calendar start day and End day with TimeSheet period Start and End day except the timesheet period which has the start and end day as Sunday-Saturday. This is because the TimeSheet side calender is a normal calendar which is hard coded into the application,there is no option available in the Web TimeSheet application to change the start day and end day of the TimeSheet side calendar to match with the TimeSheet period's start and end day.