The Calendar start and Calendar end fields are only available for French and Portuguese legislations.
These dates are used to print the detail of the time entry (leave days) on the payslip.
For example, if the calendar start and end dates are 11/27/2017 (27 November 2017) and 12/31/17 (31 December 2017), the December payslips will display a calendar from and to these dates, containing the leave detail day by day for this period.