axvspan musings

axvspan is useful with plot_date.

Two thoughts addressing only convenience not functionality.

1. Might it make sense for the first argument to be a list?
   This would be interpreted as
   allowing multiple shadings in one go. If breaking the
   interface is too costly, perhaps allowing matched lists
   for the xmin and xmax arguments would be an alternative.

2. If I wish to shade date ranges, am I right that I now
   should produce date objects and then use date2num to get
   xmin and xmax? Would it be useful for axvspan to
   directly accept the tuples that would be fed to date (or
   datetime) for xmin and xmax?

Alan Isaac