UNIX timestamp (= seconds since 1/1/1970) in document?

Question

I would like to include a so-called UNIX timestamp in my document. All technicalities aside, it's basically the number of seconds since 1/1/1970 0:00 UTC aka "the epoch". (At the time of me writing this, it's 1385812869.)

If have not found a way to include that number in my document. Unless I have overlooked something, the obvious suspects (datetime, isodate, scrtime) seem not to provide a ready-made solution.

Answer 1

pdflatex \\def\\epoch{`date +%s`}\\input ep.tex

the exact form of quoting on the command line depends on your shell (this is bash)

where ep.tex is

\documentclass{article}

\begin{document}

now = \epoch.


\end{document}

---

If you want to calculate it portably in classic TeX (actually I used etex, arithmetic but that could be easily removed) you can do this (which actually is exactly 1 day out in my system, so you could either fix my arithmetic or just add a day at the start:-)

\documentclass{article}

\begin{document}

now1 = \epoch.
\newcount\tepoch

\count0=\numexpr\year-1970\relax
\tepoch=\numexpr\count0*365*24*60*60\relax

\count2=\count0
\divide\count2 4

%extra day for each leap year (avoid complication of mod 100 and mod 400, so we are good until 2100
\advance\tepoch\numexpr\count2*24*60*60\relax

% extra whatever for each whole month
\ifnum\month>1 \advance\tepoch\numexpr 31*24*60*60\relax \fi

\ifnum\numexpr4*\count2\relax=\count0
  \ifnum\month>2 \advance\tepoch\numexpr 29*24*60*60\relax \fi
\else
  \ifnum\month>2 \advance\tepoch\numexpr 28*24*60*60\relax \fi
\fi

\ifnum\month>3 \advance\tepoch\numexpr 31*24*60*60\relax \fi
\ifnum\month>4 \advance\tepoch\numexpr 30*24*60*60\relax \fi
\ifnum\month>5 \advance\tepoch\numexpr 31*24*60*60\relax \fi
\ifnum\month>6 \advance\tepoch\numexpr 30*24*60*60\relax \fi
\ifnum\month>7 \advance\tepoch\numexpr 31*24*60*60\relax \fi
\ifnum\month>8 \advance\tepoch\numexpr 31*24*60*60\relax \fi
\ifnum\month>9 \advance\tepoch\numexpr 30*24*60*60\relax \fi
\ifnum\month>10 \advance\tepoch\numexpr 31*24*60*60\relax \fi
\ifnum\month>11 \advance\tepoch\numexpr 30*24*60*60\relax \fi

% seconds from previous days in this month
\advance\tepoch\numexpr (\day-1)*24*60*60\relax

% seconds from today
\advance\tepoch\numexpr \time*60\relax


now2 = \the\tepoch.

diff = \the\numexpr(\epoch-\tepoch)/(60*60)\relax\ hours

\end{document}

Answer 2

This works with pdflatex and lualatex, with --shell-escape; of course it's system dependent and will work only on Unix systems.

\documentclass{article}
\usepackage{catchfile}
\makeatletter
\CatchFileEdef{\epoch}{|"date -j +\@percentchar s"}{\endlinechar=\m@ne}
\CatchFileEdef{\timestamp}{|"date -j"}{\endlinechar=\m@ne}
\makeatother
\begin{document}
\epoch

\timestamp

\pdfcreationdate % this is available also without shell escape
\end{document}

Answer 3

Apart from interesting answer by David and his suggestion about calculating it manually, here is my solution based on luatex. Please note that this is just a guideline and the code is neither clean nor complete by any means. There are lots of rooms for improvements!

\documentclass{article} 
\usepackage{luacode}
\begin{luacode*}
    function epoch (format,time)
    if format == 1 then
      fmt = "%c"
    elseif format == 2 then
      fmt = "%A"
    elseif format == 3 then
      fmt = "%B"
    elseif format == 4 then
      fmt = "%X"
    else
      fmt = "%x"
    end
    tex.sprint(os.date(fmt, time))
    end
\end{luacode*}

\newcommand\epoch[2]{\directlua{epoch(#1,#2)}}

\begin{document}
This is a test. We now check the time stamp for 1385817087
\begin{itemize}
    \item \%c \epoch{1}{1385817087}
    \item \%A \epoch{2}{1385817087}
    \item \%B \epoch{3}{1385817087}
    \item \%X \epoch{4}{1385817087}
\end{itemize}
\end{document}

You have to compile this by lualatex myfile.tex. Other options for using lua function os.date can be found here.

---

---

Answer 4

To supplement that part of David Carlisle's answer which uses the POSIX date utility, here is a way to get the epoch on Windows.

On Windows the "epoch time" concept not only implemented in Unix-like environments and their utilities, but also in the standard C library functions implemented in the Microsoft Visual C Library.

That is to say, Microsoft's <time.h> material is based on a Unix-like time_t whose units are seconds, and which measures since the Epoch. This is not required by ISO C, but it helps port code which assumes that representation.

So you can make yourself some trimmed down epoch.exe with Visual C that prints the time.

I just compiled this code with VS2008 into a Win32 console application.

#include <stdio.h>
#include <time.h>

int main(void)
{
   printf("%ld\n", (long) time(0));
   return 0;
}

The statically-linked (no dependency on a msvcrt.dll) executable (156 kB) is here.