anchor.diff:  
       month_boundaries/1,
       week_boundaries/1,
  -    week_boundaries/2
  +    week_boundaries/2,
  +    
  +    timestamp_to_datetime/1,
  +    datetime_to_timestamp/1
   ]).
   
   
  
positive.code: -export([
      timesince/2,
  	timesince/3,
  	 timesince/4,
  	
  	days_in_year/1,
  	
  
negative.code:     day_add(prev_day(Date), Num + 1);
  day_add(Date, Num) when Num > 0 ->
      day_add(next_day(Date), Num - 1).
  
  
  
  %% @doc Translate UNIX timestamp to local datetime.
  timestamp_to_datetime(Seconds) ->
     BaseDate = calendar:datetime_to_gregorian_seconds({{1970,1,1},{0,0,0}}),
     calendar:universal_time_to_local_time(calendar:gregorian_seconds_to_datetime(BaseDate + Seconds)).
  
  
  %% @doc Translate a date to UNIX timestamp
  datetime_to_timestamp(?ST_JUTTEMIS) ->
      undefined;
  datetime_to_timestamp(undefined) ->
      undefined;
  datetime_to_timestamp(DT) ->
      BaseDate = calendar:datetime_to_gregorian_seconds({{1970,1,1},{0,0,0}}),
      calendar:datetime_to_gregorian_seconds(hd(calendar:local_time_to_universal_time_dst(DT))) - BaseDate.
  