Problem plotting one date with plot_date


I am having a problem with plotting a single piece of data on the graph.
This is the code I am trying to run:

a = [3]
d = [1118188800]
new_date = [dates.date2num(datetime.fromtimestamp(d[0]))]

fig = Figure()
canvas = FigureCanvasAgg(fig)
ax = fig.gca()
dayloc = dates.DayLocator()
datform = dates.DateFormatter('%b %d')

ax.plot_date(new_date, a, 'b-')
canvas.print_figure('plot.png', dpi=75)

What happens is that the date axis (x-axis) seems to get values printed very
close to each other, in fact they seems to be overlapping each other so much,
all I see is an uneven black line on the bottom of the graph where the dates
should be.

For this graph, usually there is more than one date and then I want the graph to
automatically set the range for me, but in this case I am not sure how to set
the axis to show the date I plot plus a few more on each side decently spaced.

The problem does not appear for the y-axis where it shows a few integers to each
side of '3'.

Any help with this will be appreciated.

Maria Khomenko
University of Toronto, Argon Team