(Just thinking aloud here)

We need to improve axis support for dates and times.

* Manual entry of upper/lower limits and tick sizes need to understand
  things like 00:30:00.  Note, that interpretation depends on the format
  in some cases such as "00:30" which is either 30 minutes or 30 seconds.

* We need to pick lower/upper limits sanely.  Ditto for ticks.

  This probably is not hard for time axes -- it is basically just a matter
  of different number bases being used.

  For dates, things are worse.  Limits are probably not too hard, but ticks
  will not be uniform.  If lower limit is 1-Jan-2009 and upper limit is
  31-Dec-2009, then the obvious major tick is "1 month".  If we stay in
  days-since-1900 space, then ticks are non uniform since month lengths
  differs.  We do not absolutely have to stay in that space, though.
  We could internally map to years-since-1900 and allocate 1/12 of a year
  to each month and each day the suitable fraction of the month they are
  in.

  Having such uniform months may be desirable when the axis spans more than
  2 months, but it might look weird for an axis from 29-Jan to 3-Feb.