anchor.diff:  
     INTEGER :: year
   
  +  ! TODO: d%year must be positive. Implement checks.
  +
     date2num = 0
     DO year = 1,d%year-1
       date2num = date2num+daysInYear(year)
  
positive.code: PURE ELEMENTAL SUBROUTINE addSeconds(self,s)
  !======================================================================>
  !
  ! datetime-bound procedure. It adds an integer number of seconds to 
  ! self. Called by datetime addition (+) and subtraction (-) operators.
  !
  !======================================================================>
  
  
negative.code: PURE ELEMENTAL SUBROUTINE addMinutes(self,m)
  !======================================================================>
  !
  ! datetime-bound procedure. Adds an integer number of minutes to self. 
  ! Called by datetime addition (+) and subtraction (-) operators.
  !
  !======================================================================>
  
  