When specifying times in the tags/properties matcher you can use 
relative time notation, such as <yesterday> or <-1w>.  This patch
allows this to be used in other places, such as the :tstart and :tend
parameters of clocktable.

Btw, I couldn't quite understand the exact meaning of :block, :tstart 
and :tend as decribed in the manual.  Is there a better explanation
somewhere?

thanks,

ilya