First off, to put something into the pasteboard, you use pbcopy. pbpaste is for getting stuff out.
pbcopy takes its input from stdin, so you you can do something like this:
date "+%b|%e|%g" | pbcopy
or if the date string was already in a variable you could do
echo -n $insert | pbcopy
or any of the other myriad ways to pipe something into pbcopy.
The -pboard option is used for getting/setting data of one of the named pasteboards. You then need to supply the name of a pasteboard. Without the option, the 'general' pasteboard is used.
Of course all of this is described nicely in the man pages...