anchor.diff:  
     ! ARGUMENTS:
     class(datetime),intent(in) :: d0
  -  type(datetime), intent(in) :: d1
  +  class(datetime),intent(in) :: d1
   
     type(datetime) :: d0_utc,d1_utc
   
  
positive.code:   ! ARGUMENTS:
    class(timedelta),intent(in) :: t
    class(datetime), intent(in) :: d0
    type(datetime)             :: d
  
    d = d0 + t
  
  
negative.code: !=======================================================================
  
    class(datetime),intent(in) :: d0
    class(datetime),intent(in) :: d1
    type(timedelta)            :: t
  
    real(kind=real64) :: daysDiff
    integer :: days,hours,minutes,seconds,milliseconds
  