anchor.diff:  %% @doc Provide some english date strings
   tr(label, midnight) -> "midnight";
   tr(label, noon) -> "noon";
  +%% The space is included on purpose so that it is not shown in format "e" ($e)
  +tr(label, bce) -> " BCE";
  +tr(label, ce) -> " CE";
   
   %% @doc Provide english versions of the day of the week.
   tr(dayname, 1) -> "Monday";
  
positive.code:     C =:= $c orelse
      C =:= $d orelse
      C =:= $D orelse
      C =:= $f orelse
      C =:= $F orelse
      C =:= $g orelse
  
negative.code: tag_to_value($B, _, _, _Options) ->
     ""; % NotImplementedError
  
  %% Only show era (BCE/CE) when date is BCE
  tag_to_value($e, {Y, _, _} = Date, Time, Options) when Y < 0 ->
     tag_to_value($E, Date, Time, Options);
  tag_to_value($e, _, _, _Options) ->
     "";
  
  %% Always show era (BCE/CE)
  tag_to_value($E, {Y, _, _}, _, Options) when Y < 0 ->
      tr(label, bce, Options);
  tag_to_value($E, _, _, Options) ->
      tr(label, ce, Options);
  
  %
  % Time, in 12-hour hours and minutes, with minutes
  % left off if they're zero.
  