Some timezone IDs are not supported

Using America/Fort_Nelson as timezone ID causes an exception:
2019-09-27 10:00:28 [ERROR] com.sonicle.webtop.calendar.Service - Error in GetSchedulerDates
java.lang.IllegalArgumentException: The datetime zone id 'America/Fort_Nelson' is not recognised
        at org.joda.time.DateTimeZone.forID(DateTimeZone.java:229)
        at com.sonicle.webtop.calendar.CalendarManager.listEventDates(CalendarManager.java:692)
        at com.sonicle.webtop.calendar.Service.processGetSchedulerDates(Service.java:655)
        at