anchor.diff:  Unknown : 'unknown';
   QuestionMarkTilde : '?~';
   
  +YearUA : Year UASymbol;
  +SeasonUA : Season UASymbol;
  +YearMonthUA : YearMonth UASymbol;
  +YearMonthDayUA : YearMonthDay UASymbol;
  +
   Season : Year Dash ('21' | '22' | '23' | '24');
   UASymbol : QuestionMark | Tilde | QuestionMarkTilde;
   YearWithOneUnspecifedDigit : Digit Digit Digit U;
  
positive.code:     | ( '04' | '06' | '09' | '11' ) Dash OneThru30
      | '02' Dash OneThru29
      ;
  
  YearMonthDay : Year Dash MonthDay;
  Day : OneThru31;
  Hour : ZeroThru23;
  
negative.code: 	| OpenParen Year CloseParen Dash MonthDay UASymbol
  	;
  YearKnownMonthDayUAParenUA : OpenParen YearKnownMonthDayUA CloseParen UASymbol;
  YearMonthKnownDayUA : YearMonth Dash OpenParen Day CloseParen UASymbol;
  YearMonthKnownDayUAParenUA : OpenParen YearMonthKnownDayUA CloseParen UASymbol;
  DayKnownYearMonthUA
  	: YearMonth UASymbol Dash Day
  	| Year UASymbol Dash Month UASymbol Dash Day
  	;
  DayKnownYearMonthUAParenUA : OpenParen DayKnownYearMonthUA CloseParen UASymbol;
  YearKnownMonthUA : Year Dash OpenParen Month CloseParen UASymbol;
  YearKnownMonthUAParenUA : OpenParen YearKnownMonthUA CloseParen UASymbol;
  Level2YearMonthUA : Year UASymbol Dash OpenParen Month CloseParen UASymbol;
  Level2YearMonthUAParenUA : OpenParen YearMonthUA CloseParen UASymbol;
  Level2YearMonthDayUA : OpenParen Year CloseParen UASymbol Dash Month Dash Day UASymbol;
  Level2YearMonthDayUAParenUA : OpenParen YearMonthDayUA CloseParen UASymbol;
  MonthKnownYearUA : Year UASymbol Dash Month;
  MonthKnownYearUAParenUA : OpenParen MonthKnownYearUA CloseParen UASymbol;
  
  // ***********************   Level 2: Parser Rules   ************************ //
  
  