I've seen (I don't know where) a couple of interesting metadata-oriented control sequences, and I was wondering if such a sequence exists for the job runtime. I can't expect it to give me the total run-time, but the run-time at that specific point would work well enough. I'm putting in a rather braggy colophon, for the interested.
My use case would be something like
\documentclass{silly}
\usepackage{mwe}
\begin{document}
\lipsum\lipsum\lipsum
This document was typeset with \XeTeX, which is based on the \TeX\ typesetting
system by Dr.~Donald~Knuth... which is very fast. This entire work took only
\pdfjobtime\ seconds to compile!
\end{document}
\pdfelapsedtimefor LuaTeX and XeTeX – Werner Jul 17 '13 at 20:50