Biblatex Tester, Basic Examples. Tests style=authoryear, mergedate bugs.

Biblatex-Tester-BasicExamples.bib

% Common - Typical

@article{chalmers_1995_typical,
  author = {Chalmers, David J.},
  date = {1995},
  title = {Typical citation of a modern work},
}


% Common - Approximate and uncertain

@book{galilei_1590_approximate,
  author = {Galilei, Galileo},
  date = {1590~},
  title = {Approximate, circa 'ca.'},
}

@book{aquinas_1256_uncertain,
  author = {Aquinas, Thomas},
  date = {1256?},
  title = {Uncertain},
}

@book{aquinas_1273_approximate_and_uncertain,
  author = {Aquinas, Thomas},
  date = {1273?~},
  title = {Approximate and uncertain},
}


% Common - eras

@book{plato_2004_eras_bce,
  author = {{Plato}},
  date = {-0379~},
  title = {Eras, before the year zero, 'BCE'},
}

@book{epictetus_1916_eras_ce,
  author = {{Epictetus}},
  date = {0125~},
  title = {Eras, not long after the year zero, 'CE'},
}


% Precision finer than a year - Times

@book{simpson_2016_time_unspecified_timezone,
  author = {Simpson, Lisa},
  date = {2016-07-18T10:26:06},
  title = {Time, unspecified time zone},
}

@article{barker_2016_time_local_timezone,
  author = {Barker, Anne},
  date = {2016-06-06T18:20:00+10:00},
  title = {Time, local time zone},
}

@book{simpson_2016_time_zulu_timezone,
  author = {Simpson, Lisa},
  date = {2016-07-18T20:26:06Z},
  title = {Time, zulu time zone},
}


% Precision finer than a year - Dates

@article{kennett_2008_date_month,
  author = {Kennett, Jeanette},
  date = {2008-01},
  title = {Month precision date},
}

@article{mendelsohn_2010__date_day,
  author = {Mendelsohn, Daniel},
  date = {2010-01-25},
  title = {Day precision date.},
}


% Precision finer than a year - Season

@book{sep_2016_season,
  author = {{SEP}},
  date = {2016-23},
  title = {Season precision},
}

Biblatex-Tester-BasicExamples.tex

\documentclass[12pt,a4paper]{article}

\PassOptionsToPackage{%
    %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
    % Dates and Datetimes
    %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
    % julian=true,% convert dates before gregorianstart to Julian Calendar
    % gregorianstart=1582-10-15,% Default
    alldates=ymd, % year, short, long, terse, comp, ymd, edtf. ymd = Year-Month-Day format
    labeldate=year, % year, short, long, terse, comp, ymd, edtf. ymd = Year-Month-Day format
    alldatesusetime=true, % print time components in non-compact date ranges
    labeldateusetime=false,
    alltimes=24h, % 12h, 24h, 24hcomp. 
    seconds=false, 
    timezones=true,
    datezeros=true,
    % dateera=astronomical (default), secular, christian
    %   astronomical dates, controlled by datezero
    %   secular (prints BCE/CE) controlled by dateerauto, datezeros
    %   christian prints BC/AD controlled by dateerauto, datezeros
    dateera=secular,
    dateeraauto=501, % Sets the max year ceiling for automatic printing of era
    abbreviate=true, % prints full localisation strings
    dateabbrev=false, % prints full date localisation strings
    dateuncertain=true,
    datecirca=true,
    %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
    % Style
    %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
    style=authoryear,
    sorting=none,
    dashed=false,
    url=false,
    %refsection=section,
    %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
    % style=authoryear option
    %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
    % mergedate=  % false, minimum, basic, compact or true (default), maximum.
    %    See \doc\latex\biblatex\examples\50-style-authoryear-biber.pdf
    % mergedate bug tests: 
    %   alldates=ymd,
    %   labeldate=year,
    %       false (1,2), minimum (1,2), basic (1,2), compact (1,2:Fail?), true (1,2:Fail?), maximum (1,2:Fail?)    
    %   alldates=ymd, 
    %   labeldate=ymd
    %       false (), minimum (), basic (), compact (), true (), maximum ()
    mergedate=true    
}{biblatex}
\usepackage{biblatex}
\addbibresource{Biblatex-Tester-BasicExamples.bib}

% Seperation between time and timezone.
\DefineBibliographyExtras{english}{
  \renewcommand*{\bibtimezonesep}{\space}
}

% Remove paragraph first line indenting for easy comparison
\setlength{\parindent}{0pt}

% Convenience command
\newcommand{\mycite}[1]{Lorem \autocite{#1}. \citetitle{#1}.\\}

\begin{document}

\begin{refsection}  
  \section{Common}
  \subsection{Citations}
  Typical:\\
  \mycite{chalmers_1995_typical}
  
  Approximate and uncertain:\\
  \mycite{galilei_1590_approximate}
  \mycite{aquinas_1256_uncertain}
  \mycite{aquinas_1273_approximate_and_uncertain}
  
  Eras:\\
  \mycite{plato_2004_eras_bce}
  \mycite{epictetus_1916_eras_ce}
  
  \printbibliography[heading=subbibnumbered]
\end{refsection}

\clearpage
\begin{refsection}  
  \section{Precision finer than a year}
  \subsection{Citations}
  Times:\\
  \mycite{simpson_2016_time_unspecified_timezone}
  \mycite{barker_2016_time_local_timezone}
  \mycite{simpson_2016_time_zulu_timezone}
  
  Precision finer than a year - Dates:\\
  \mycite{kennett_2008_date_month}
  \mycite{mendelsohn_2010__date_day}
  
   Precision finer than a year - Season:\\
  \mycite{sep_2016_season}
  
  \printbibliography[heading=subbibnumbered]
\end{refsection}


\end{document}