anchor.diff:  // ********************  Level 2: Interval Parser Rules  ******************** //
   
   level2Interval
  -    : dateOrSeason Slash dateWithPartialUncertainty
  -    | dateWithPartialUncertainty Slash dateOrSeason
  -    | dateWithPartialUncertainty Slash dateWithPartialUncertainty
  -    ;
  -dateWithPartialUncertainty
  -    : partialUncertainOrApproximate
  -    | partialUnspecified
  +    : dateOrSeason Slash (partialUA | partialUnspecified)
  +    | (partialUA | partialUnspecified) Slash dateOrSeason
  +    | (partialUA | partialUnspecified) Slash (partialUA | partialUnspecified)
       ;
positive.code:     ;
  listElement
      : date
      | dateWithPartialUncertainty
      | uncertainOrApproxDate
      | unspecifiedDate
      | consecutives
  
negative.code:     | DigitOrU DigitOrU U DigitOrU
      | DigitOrU DigitOrU DigitOrU U
      ;
  YearMonthWithU
  	: Year Dash MonthWithU
  	| YearWithU Dash MonthWithU
  	| YearWithU Dash Month
  	;
  MonthWithU : ZeroU | OneU | U DigitOrU;
  DayWithU : U DigitOrU | OneThru3 U;
  YearMonthDayWithU
  