Теперь я использую версию JTAppCalendar 6.0,
func configureCalendar(_ calendar: JTAppleCalendarView) -> ConfigurationParameters {
let formatter = DateFormatter()
formatter.dateFormat = "yyyy MM dd"
let parameters = ConfigurationParameters(startDate: startDate,
endDate: endDate,
numberOfRows: 6,
calendar: testCalendar, // This parameter will be removed in version 6.0
generateInDates: .forAllMonths,
generateOutDates: .tillEndOfGrid,
firstDayOfWeek: .sunday)
return parameters
}