@comment{
    - Dates
    - Not included in tests:
        - malformed dates and date ranges
        - literal dates ("13th century"; not supported by biblatex)
        - seasons (would have to come from parsing the issue field)
        - uncertain dates (use "doubtfuldate" from biblatex-apa?)
        - dates with single-digit day or month (not supported by biblatex)
        - negative dates (not supported by biblatex)
    - Note: biblatex supports years < 1000 but only if padded with leading zeros
    - TODO:
        - either biblio2yaml or, probably better, citeproc should strip leading zeros
         from days and months (CSL can add leading zeros to its output, but not remove
         them when they are in its input data)
}

@article{year-month-old,
    Author = {Author, Al},
    Journal = {Journal},
    Month = aug,
    Title = {Year and Month, bibtex style, supported by biblatex for backwards compatibility},
    Year = {1999}}

@article{year-month-new,
    Author = {Author, Al},
    Journal = {Journal},
    Month = {08},
    Title = {Year and Month, biblatex style; note that biblatex does not have a ``day'' field},
    Year = {1999}}

@article{dates,
    Author = {Author, Al},
    Date = {2012-12-13},
    Eventdate = {2011-10-03},
    Journal = {Journal},
    Month = may,
    Origdate = {1888-10-01},
    Title = {Dates, default biblatex style; year, month to be ignored if date exists},
    Urldate = {1999-05-23},
    Year = {9999}}

@article{date-ranges-different-years,
    Author = {Author, Al},
    Date = {1999-10-14/2010-01-23},
    Eventdate = {1999-12/2000-01},
    Journal = {Journal},
    Origdate = {1888-01-02/1913-12-13},
    Title = {Date ranges; different years},
    Urldate = {2012-10-12/2013-01-31}}

@article{date-ranges-same-year,
    Author = {Author, Al},
    Date = {1999-10-14/1999-10-15},
    Eventdate = {1999-10/1999-11},
    Journal = {Journal},
    Origdate = {1888-01-02/1888-12-13},
    Title = {Date ranges; same year},
    Urldate = {2012-10-31/2012-11-01}}

@article{date-ranges-open,
    Author = {Author, Al},
    Date = {1999-10-14/},
    Eventdate = {1999-10/},
    Journal = {Journal},
    Origdate = {1888-01-02/},
    Title = {Date ranges, open-ended},
    Urldate = {2012-10-31/}}

@article{dates-very-old,
    Author = {Author, Al},
    Date = {0712-12-13},
    Eventdate = {0311-10-03},
    Journal = {Journal},
    Month = may,
    Origdate = {0088-10-01},
    Title = {Dates, year less than 1000},
    Urldate = {0999-12-14}}

---
references:
- id: year-month-old
  type: article-journal
  author:
  - family: Author
    given: Al
  issued:
  - year: 1999
    month: 8
  title: Year and month, bibtex style, supported by biblatex for backwards compatibility
  container-title: Journal

- id: year-month-new
  type: article-journal
  author:
  - family: Author
    given: Al
  issued:
  - year: 1999
    month: 8
  title: Year and month, biblatex style; note that biblatex does not have a “day”
    field
  container-title: Journal

- id: dates
  type: article-journal
  author:
  - family: Author
    given: Al
  issued:
  - year: 2012
    month: 12
    day: 13
  event-date:
  - year: 2011
    month: 10
    day: 3
  accessed:
  - year: 1999
    month: 5
    day: 23
  original-date:
  - year: 1888
    month: 10
    day: 1
  title: Dates, default biblatex style; year, month to be ignored if date exists
  container-title: Journal

- id: date-ranges-different-years
  type: article-journal
  author:
  - family: Author
    given: Al
  issued:
  - year: 1999
    month: 10
    day: 14
  - year: 2010
    month: 1
    day: 23
  event-date:
  - year: 1999
    month: 12
  - year: 2000
    month: 1
  accessed:
  - year: 2012
    month: 10
    day: 12
  - year: 2013
    month: 1
    day: 31
  original-date:
  - year: 1888
    month: 1
    day: 2
  - year: 1913
    month: 12
    day: 13
  title: Date ranges; different years
  container-title: Journal

- id: date-ranges-same-year
  type: article-journal
  author:
  - family: Author
    given: Al
  issued:
  - year: 1999
    month: 10
    day: 14
  - year: 1999
    month: 10
    day: 15
  event-date:
  - year: 1999
    month: 10
  - year: 1999
    month: 11
  accessed:
  - year: 2012
    month: 10
    day: 31
  - year: 2012
    month: 11
    day: 1
  original-date:
  - year: 1888
    month: 1
    day: 2
  - year: 1888
    month: 12
    day: 13
  title: Date ranges; same year
  container-title: Journal

- id: date-ranges-open
  type: article-journal
  author:
  - family: Author
    given: Al
  issued:
  - year: 1999
    month: 10
    day: 14
  - {}
  event-date:
  - year: 1999
    month: 10
  - {}
  accessed:
  - year: 2012
    month: 10
    day: 31
  - {}
  original-date:
  - year: 1888
    month: 1
    day: 2
  - {}
  title: Date ranges, open-ended
  container-title: Journal

- id: dates-very-old
  type: article-journal
  author:
  - family: Author
    given: Al
  issued:
  - year: 712
    month: 12
    day: 13
  event-date:
  - year: 311
    month: 10
    day: 3
  accessed:
  - year: 999
    month: 12
    day: 14
  original-date:
  - year: 88
    month: 10
    day: 1
  title: Dates, year less than 1000
  container-title: Journal
...