anchor.diff:  
   `date_hour` or `strict_date_hour`::
   
  -    A formatter that combines a full date and two digit hour of day.
  +    A formatter that combines a full date and two digit hour of day:
  +    `yyyy-MM-dd'T'HH`.
   
   `date_hour_minute` or `strict_date_hour_minute`::
   
       A formatter that combines a full date, two digit hour of day, and two
  -    digit minute of hour.
  +    digit minute of hour: `yyyy-MM-dd'T'HH:mm`.
   
   `date_hour_minute_second` or `strict_date_hour_minute_second`::
   
       A formatter that combines a full date, two digit hour of day, two digit
  -    minute of hour, and two digit second of minute.
  +    minute of hour, and two digit second of minute: `yyyy-MM-dd'T'HH:mm:ss`.
   
   `date_hour_minute_second_fraction` or `strict_date_hour_minute_second_fraction`::
   
  
positive.code: 
  `hour` or `strict_hour`::
  
      A formatter for a two digit hour of day.
  
  `hour_minute` or `strict_hour_minute`::
  
      A formatter for a two digit hour of day and two digit minute of hour.
  
  `hour_minute_second` or `strict_hour_minute_second`::
  
      A formatter for a two digit hour of day, two digit minute of hour, and two
      digit second of minute.
  
  `hour_minute_second_fraction` or `strict_hour_minute_second_fraction`::
  
  
negative.code: 
  `weekyear` or `strict_weekyear`::
  
      A formatter for a four digit weekyear: `xxxx`.
  
  `weekyear_week` or `strict_weekyear_week`::
  
      A formatter for a four digit weekyear and two digit week of weekyear:
      `xxxx-'W'ww`.
  
  `weekyear_week_day` or `strict_weekyear_week_day`::
  
      A formatter for a four digit weekyear, two digit week of weekyear, and one
      digit day of week: `xxxx-'W'ww-e`.
  
  `year` or `strict_year`::
  
      A formatter for a four digit year: `yyyy`.
  
  `year_month` or `strict_year_month`::
  
      A formatter for a four digit year and two digit month of year: `yyyy-MM`.
  
  `year_month_day` or `strict_year_month_day`::
  
      A formatter for a four digit year, two digit month of year, and two digit
      day of month: `yyyy-MM-dd`.
  
  