\ctxloadluafile{getdate}

\def\getdate
  {\dosingleempty\dogetdate}

\def\dogetdate[#1]%
  {\ctxlua{context(documentdata.modification_date("\jobname.tex", "#1"))}}

\def\Testall{%
  \starttabulate[|r|l|]
    \NC nice  \NC {\os\getdate[nice]} \AR
    \NC long  \NC {\os\getdate[long]} \AR
    \NC plain \NC {\os\getdate}       \AR   
  \stoptabulate
  \hairline%
}

\starttext

\Testall

\language[de]
\Testall

\language[nl]
\Testall

\language[it]
\Testall

\language[no]
\Testall

\stoptext