def remove_recurrence_time(time)
      found = false
      @all_recurrence_rules.delete_if do |rule|
        found = true if rule.is_a?(SingleOccurrenceRule) && rule.time == time
      end
      time if found
    end
def remove_recurrence_time(time)
      found = false
      @all_recurrence_rules.delete_if do |rule|
        found = true if rule.is_a?(SingleOccurrenceRule) && rule.time == time
      end
      time if found
    end
Remove a recurrence time