sorting dates in tables
> I don't quite get the example regarding sorting dates in a table. Who would want an extra table with the sortkey displayed?
I don't know either but the function is available at least since 1.7.1  and returns the JD of the date which is also used internally to sort dates.
> I have seen SMW doing it wrong
Where and in which context?
> So why would I need #SORTKEY and how would I use it?
 is the PR that introduced the output format and notes "new output format "sortkey" to help people who want to handcraft sortable tables containing date values".