anchor.diff:  
   MonthDayKnownYearUA : Year UASymbol Dash MonthDay UASymbol?;
   MonthDayKnownYearUAParenUA : OpenParen MonthDayKnownYearUA CloseParen UASymbol;
  -MonthKnownYearDayUA : Year UASymbol Dash Month Dash OpenParen Day CloseParen UASymbol;
  +MonthKnownYearDayUA
  +	: Year UASymbol Dash Month Dash OpenParen Day CloseParen UASymbol
  +	;
   MonthKnownYearDayUAParenUA : OpenParen MonthKnownYearDayUA CloseParen UASymbol;
   YearDayKnownMonthUA : Year Dash OpenParen Month CloseParen UASymbol Dash Day;
   YearDayKnownMonthUAParenUA : OpenParen YearDayKnownMonthUA CloseParen UASymbol;
  
positive.code: // ********************  Level 2: Interval Parser Rules  ******************** //
  
  level2Interval
      : dateOrSeason Slash dateWithPartialUncertainty
      | dateWithPartialUncertainty Slash dateOrSeason
      | dateWithPartialUncertainty Slash dateWithPartialUncertainty
      ;
  dateWithPartialUncertainty
      : partialUncertainOrApproximate
      | partialUnspecified
      ;
negative.code:     ;
  listElement
      : date
      | partialUA
      | partialUnspecified
      | uncertainOrApproxDate
      | unspecifiedDate
      | consecutives
  