@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:
- title: Year and month, bibtex style, supported by biblatex for backwards compatibility
  id: year-month-old
  issued:
    month: 08
    year: 1999
  author:
    given:
    - Al
    family: Author
  container-title: Journal
  type: article-journal
- title: Year and month, biblatex style; note that biblatex does not have a “day”
    field
  id: year-month-new
  issued:
    month: 08
    year: 1999
  author:
    given:
    - Al
    family: Author
  container-title: Journal
  type: article-journal
- original-date:
    day: 01
    month: 10
    year: 1888
  title: Dates, default biblatex style; year, month to be ignored if date exists
  event-date:
    day: 03
    month: 10
    year: 2011
  id: dates
  issued:
    day: 13
    month: 12
    year: 2012
  author:
    given:
    - Al
    family: Author
  accessed:
    day: 23
    month: 05
    year: 1999
  container-title: Journal
  type: article-journal
- original-date:
  - day: 02
    month: 01
    year: 1888
  - day: 13
    month: 12
    year: 1913
  title: Date ranges; different years
  event-date:
  - month: 12
    year: 1999
  - month: 01
    year: 2000
  id: date-ranges-different-years
  issued:
  - day: 14
    month: 10
    year: 1999
  - day: 23
    month: 01
    year: 2010
  author:
    given:
    - Al
    family: Author
  accessed:
  - day: 12
    month: 10
    year: 2012
  - day: 31
    month: 01
    year: 2013
  container-title: Journal
  type: article-journal
- original-date:
  - day: 02
    month: 01
    year: 1888
  - day: 13
    month: 12
    year: 1888
  title: Date ranges; same year
  event-date:
  - month: 10
    year: 1999
  - month: 11
    year: 1999
  id: date-ranges-same-year
  issued:
  - day: 14
    month: 10
    year: 1999
  - day: 15
    month: 10
    year: 1999
  author:
    given:
    - Al
    family: Author
  accessed:
  - day: 31
    month: 10
    year: 2012
  - day: 01
    month: 11
    year: 2012
  container-title: Journal
  type: article-journal
- original-date:
  - day: 02
    month: 01
    year: 1888
  - {}
  title: Date ranges, open-ended
  event-date:
  - month: 10
    year: 1999
  - {}
  id: date-ranges-open
  issued:
  - day: 14
    month: 10
    year: 1999
  - {}
  author:
    given:
    - Al
    family: Author
  accessed:
  - day: 31
    month: 10
    year: 2012
  - {}
  container-title: Journal
  type: article-journal
- original-date:
    day: 01
    month: 10
    year: 0088
  title: Dates, year less than 1000
  event-date:
    day: 03
    month: 10
    year: 0311
  id: dates-very-old
  issued:
    day: 13
    month: 12
    year: 0712
  author:
    given:
    - Al
    family: Author
  accessed:
    day: 14
    month: 12
    year: 0999
  container-title: Journal
  type: article-journal
...