documentclass{standalone}
usepackage{pgfplots}
pgfplotsset{compat=1.14}
usepgfplotslibrary{dateplot}

newcommand{dateticks}{
  foreach i in {1,...,11}
    {ifnumi<10
       2016-0i-01,%
     else
       2016-i-01,%
     fi
       2016-12-01
     }
}

begin{document}
begin{tikzpicture}
begin{axis}[
date coordinates in=x,
%xtick={dateticks},        % <- This doesn't work
xtick={2016-01-01,2016-02-01,2016-03-01,2016-04-01,2016-05-01,2016-06-01,%
       2016-07-01,2016-08-01,2016-09-01,2016-10-01,2016-11-01,2016-12-01},
xticklabel=day/month,
xticklabel style={rotate=90},
]
addplot coordinates {(2016-01-23,10) (2016-03-05,20) (2016-09-14,10)};
end{axis}
end{tikzpicture}
end{document}

newcommandmygraph[1]{... xtick={#1} ...}

expandaftermygraphexpandafter{dateticks}

newcommanddateticks{2016-01-01}
foreach i in {2,...,12}{xdefdateticks{dateticks,2016-ifnumi<10 0fii-01}}

documentclass{article}
usepackage{pgfplots}
pgfplotsset{compat=1.14}
usepgfplotslibrary{dateplot}
newcommanddateticks{2016-01-01}
foreach i in {2,...,12}{xdefdateticks{dateticks,2016-ifnumi<10 0fii-01}}
newcommandmygraph[1]%
  {begin{tikzpicture}
    begin{axis}%
      [date coordinates in=x,
       xtick={#1},
       xticklabel=day/month,
       xticklabel style={rotate=90},
      ]
      addplot coordinates {(2016-01-23,10) (2016-03-05,20) (2016-09-14,10)};
    end{axis}
   end{tikzpicture}%
  }
begin{document}
expandaftermygraphexpandafter{dateticks}
end{document}

setdateticks{YYYY-MM-DD}{N}

newcommanddateticks{}
newcommandsplitdate{}
defsplitdate#1-#2#3-#4-%
  {defYYYY{#1}%
   ifnum#2=0defMM{#3}elsedefMM{#2#3}fi
   defDD{#4}%
  }
newcommandsetdateticks[2]%
  {defdateticks{#1}%
   bgroup
   splitdate#1-%
   foreach i in {2,...,#2}
     {pgfmathtruncatemacromm{mod(MM+i-2,12)+1}%
      pgfmathtruncatemacroyyyy{YYYY+divide(MM+i-2,12)}%
      xdefdateticks{dateticks,yyyy-ifnummm<10 0fimm-DD}%
     }%
   egroup
  }

documentclass{article}
usepackage{pgfplots}
pgfplotsset{compat=1.14}
usepgfplotslibrary{dateplot}
newcommanddateticks{}
defsplitdate#1-#2#3-#4-%
  {defYYYY{#1}%
   ifnum#2=0defMM{#3}elsedefMM{#2#3}fi
   defDD{#4}%
  }
newcommandsetdateticks[2]%
  {defdateticks{#1}%
   bgroup
   splitdate#1-%
   foreach i in {2,...,#2}
     {pgfmathtruncatemacromm{mod(MM+i-2,12)+1}%
      pgfmathtruncatemacroyyyy{YYYY+divide(MM+i-2,12)}%
      xdefdateticks{dateticks,yyyy-ifnummm<10 0fimm-DD}%
     }%
   egroup
  }
newcommandmygraph[1]%
  {begin{tikzpicture}
    begin{axis}%
      [date coordinates in=x,
       xtick={#1},
       xticklabel=day/month,
       xticklabel style={rotate=90},
      ]
      addplot coordinates {(2016-01-23,10) (2016-03-05,20) (2016-09-14,10)};
    end{axis}
   end{tikzpicture}%
  }
begin{document}
setdateticks{2016-01-01}{12}
expandaftermygraphexpandafter{dateticks}
end{document}

documentclass{standalone}
usepackage{pgfplots}
pgfplotsset{compat=1.14}
usepgfplotslibrary{dateplot}

begin{document}
defdateticks{2016-01-01}
foreach i in {2,...,12}
  {xdefdateticks{dateticks,2016-ifnumi<10 0fii-01}}

begin{tikzpicture}
begin{axis}[
  date coordinates in=x,
  xtick/.expanded={dateticks},
  xticklabel=day/month,
  xticklabel style={rotate=90},
]
addplot coordinates {(2016-01-23,10) (2016-03-05,20) (2016-09-14,10)};
end{axis}
end{tikzpicture}
end{document}