Copy date and time of KDE calender in text format to clipboard

Is there a way to set a shortcut-key for copying a text format of current date and time of KDE environment's calender?

Why do you intend to use KDE Calendar for such a simple task? Why not to define a global shortcut

System Setting › Shortcuts and Gestures › Custom Shortcuts › Edit › New › Global Shortcut › Command / URL

for

date | xsel -i -b

?

You may use any imaginable date format if default (Fri Dec 20 09:33:37 MSK 2013) does not suite you, see date(1). E. g. date '+%F %T' will generate lexicographically sortable 2013-12-20 09:33:59.

Instead of xsel -i -b you also can use xclip -i -selection clipboard.

I assume you want to copy to CLIPBOARD. Use just xsel -i or xclip -i if you want to put date to PRIMARY selection.