Thanks.
LOGBACK-969
commits e64dc7a5c30 and dec77397c

after

CharSequenceToRegexMapper.java findMinMaxLengthsInSymbols() return min's value is always

  DateFormatSymbols symbols = DateFormatSymbols.getInstance();
  String[] symbolArray = symbols.getShortMonths();
  for(String symbol : symbolArray ){
    System.out.println("[]" + symbol);
  }

It look like DateFormatSymbols getShortMonth() , getWeekdays() ... etc..
All of function return array[last] is null

Thanks