code: private static CronDefinition cron4j() {
          return CronDefinitionBuilder.defineCron()
                  .withMinutes().and()
                  .withHours().and()
                  .withDayOfMonth().supportsL().and()
                  .withMonth().and()
                  .withDayOfWeek().withValidRange(0, 6).withMondayDoWValue(1).and()
                  .enforceStrictRanges()
                  .matchDayOfWeekAndDayOfMonth()
                  .instance();
      }
docs: Creates CronDefinition instance matching cron4j specification.
  
  @return CronDefinition instance, never null;