src/main/java/com/conveyal/gtfs/stats/FeedStats.java
public LocalDate getCalendarServiceRangeStart() {

        int startDate = 0;
        for (Service service : feed.services.values()) {
            if (service.calendar == null)
                continue;
//            if (startDate == 0 || service.calendar.start_date < startDate) {
//                startDate = service.calendar.start_date;
//            }
        }
        if (startDate == 0)
            return null;

        DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyyMMdd");
        return LocalDate.parse(String.valueOf(startDate), formatter);
    }
public LocalDate getCalendarServiceRangeStart() {

        int startDate = 0;
        for (Service service : feed.services.values()) {
            if (service.calendar == null)
                continue;
//            if (startDate == 0 || service.calendar.start_date < startDate) {
//                startDate = service.calendar.start_date;
//            }
        }
        if (startDate == 0)
            return null;

        DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyyMMdd");
        return LocalDate.parse(String.valueOf(startDate), formatter);
    }
returns null for schedules without calendar service schedules