Give date as iso format

Question

Currently, when I use \date{} for an old document, I put the explicit form of the date. But this is a problem because I print all my documents in two versions, a personal version (with the form ) and a public one with the default settings.

So, I just want to give the date in a ISO format (YYYY-MM-DD) and, depending of the global settings, all dates in the document have to follow one format.

So, I ask if there is a kind of \displaydate command witch take as argument the date in ISO format and display it according to the global setting.

So there is a package like that?

Answer 1

Use datetime2 where you can define your date styles and interchange them within your document (or globally) via \DTMsetdatestyle{<style>}:

\documentclass{article}

\usepackage[english]{datetime2}

\DTMnewdatestyle{dashdate}{%
  \renewcommand{\DTMdisplaydate}[4]{\number##1-\DTMenglishshortmonthname{##2}-\number##3}%
  \renewcommand{\DTMDisplaydate}{\DTMdisplaydate}%
}

\begin{document}

\DTMsetdatestyle{iso}
\today% ...or \DTMtoday

\DTMsetdatestyle{dashdate}
\today% ...or \DTMtoday

\DTMdisplaydate{2015}{1}{1}{-1}% Ignore Day-Of-Week

\end{document}

\DTMdisplaydate{<year>}{<month>}{<day>}{<dow>} will display a hard-coded date in the current style.