grabbing items from display buffer

[knubee]

What is the trick for being able to select/copy items that appear in
the display mini-buffer?

Example: in calendar-mode, "p c" returns "IS0 date: Day 7 of week 37 of
2005"

My attempts to move point to the mini display buffer to copy the string
"ISO etc." result in the value vanishing.

(I'm using emacs 21.3.1 if that makes any difference.)

thanks.