import matplotlib as mplimport matplotlib.pyplot as pltimport datetimeplt.switch_backend('agg')#plt.switch_backend('qt4agg')x = [datetime.datetime(2013,12,i) for i in range(1, 11)]y = range(len(x))plt.plot_date(x,y)

  File "D:/Python/untitled1.py", line 19, in <module>    plt.plot_date(x,y)  File "C:\WinPython-64bit-2.7.10.3\python-2.7.10.amd64\lib\site-packages\matplotlib\pyplot.py", line 3173, in plot_date    data=data, **kwargs)  File "C:\WinPython-64bit-2.7.10.3\python-2.7.10.amd64\lib\site-packages\matplotlib\__init__.py", line 1812, in inner    return func(ax, *args, **kwargs)  File "C:\WinPython-64bit-2.7.10.3\python-2.7.10.amd64\lib\site-packages\matplotlib\axes\_axes.py", line 1494, in plot_date    ret = self.plot(x, y, fmt, **kwargs)  File "C:\WinPython-64bit-2.7.10.3\python-2.7.10.amd64\lib\site-packages\matplotlib\__init__.py", line 1812, in inner    return func(ax, *args, **kwargs)  File "C:\WinPython-64bit-2.7.10.3\python-2.7.10.amd64\lib\site-packages\matplotlib\axes\_axes.py", line 1424, in plot    for line in self._get_lines(*args, **kwargs):  File "C:\WinPython-64bit-2.7.10.3\python-2.7.10.amd64\lib\site-packages\matplotlib\axes\_base.py", line 386, in _grab_next_args    for seg in self._plot_args(remaining, kwargs):  File "C:\WinPython-64bit-2.7.10.3\python-2.7.10.amd64\lib\site-packages\matplotlib\axes\_base.py", line 364, in _plot_args    x, y = self._xy_from_xy(x, y)  File "C:\WinPython-64bit-2.7.10.3\python-2.7.10.amd64\lib\site-packages\matplotlib\axes\_base.py", line 197, in _xy_from_xy    bx = self.axes.xaxis.update_units(x)  File "C:\WinPython-64bit-2.7.10.3\python-2.7.10.amd64\lib\site-packages\matplotlib\axis.py", line 1394, in update_units    self._update_axisinfo()  File "C:\WinPython-64bit-2.7.10.3\python-2.7.10.amd64\lib\site-packages\matplotlib\axis.py", line 1412, in _update_axisinfo    self.set_major_locator(info.majloc)  File "C:\WinPython-64bit-2.7.10.3\python-2.7.10.amd64\lib\site-packages\matplotlib\axis.py", line 1513, in set_major_locator    self.stale = True  File "C:\WinPython-64bit-2.7.10.3\python-2.7.10.amd64\lib\site-packages\matplotlib\artist.py", line 267, in stale    self.stale_callback(self, val)  File "C:\WinPython-64bit-2.7.10.3\python-2.7.10.amd64\lib\site-packages\matplotlib\artist.py", line 74, in _stale_axes_callback    self.axes.stale = val  File "C:\WinPython-64bit-2.7.10.3\python-2.7.10.amd64\lib\site-packages\matplotlib\artist.py", line 267, in stale    self.stale_callback(self, val)  File "C:\WinPython-64bit-2.7.10.3\python-2.7.10.amd64\lib\site-packages\matplotlib\figure.py", line 56, in _stale_figure_callback    self.figure.stale = val  File "C:\WinPython-64bit-2.7.10.3\python-2.7.10.amd64\lib\site-packages\matplotlib\artist.py", line 267, in stale    self.stale_callback(self, val)  File "C:\WinPython-64bit-2.7.10.3\python-2.7.10.amd64\lib\site-packages\matplotlib\pyplot.py", line 568, in _auto_draw_if_interactive    fig.canvas.draw_idle()  File "C:\WinPython-64bit-2.7.10.3\python-2.7.10.amd64\lib\site-packages\matplotlib\backend_bases.py", line 2026, in draw_idle    self.draw(*args, **kwargs)  File "C:\WinPython-64bit-2.7.10.3\python-2.7.10.amd64\lib\site-packages\matplotlib\backends\backend_agg.py", line 474, in draw    self.figure.draw(self.renderer)  File "C:\WinPython-64bit-2.7.10.3\python-2.7.10.amd64\lib\site-packages\matplotlib\artist.py", line 61, in draw_wrapper    draw(artist, renderer, *args, **kwargs)  File "C:\WinPython-64bit-2.7.10.3\python-2.7.10.amd64\lib\site-packages\matplotlib\figure.py", line 1159, in draw    func(*args)  File "C:\WinPython-64bit-2.7.10.3\python-2.7.10.amd64\lib\site-packages\matplotlib\artist.py", line 61, in draw_wrapper    draw(artist, renderer, *args, **kwargs)  File "C:\WinPython-64bit-2.7.10.3\python-2.7.10.amd64\lib\site-packages\matplotlib\axes\_base.py", line 2324, in draw    a.draw(renderer)  File "C:\WinPython-64bit-2.7.10.3\python-2.7.10.amd64\lib\site-packages\matplotlib\artist.py", line 61, in draw_wrapper    draw(artist, renderer, *args, **kwargs)  File "C:\WinPython-64bit-2.7.10.3\python-2.7.10.amd64\lib\site-packages\matplotlib\axis.py", line 1106, in draw    ticks_to_draw = self._update_ticks(renderer)  File "C:\WinPython-64bit-2.7.10.3\python-2.7.10.amd64\lib\site-packages\matplotlib\axis.py", line 949, in _update_ticks    tick_tups = [t for t in self.iter_ticks()]  File "C:\WinPython-64bit-2.7.10.3\python-2.7.10.amd64\lib\site-packages\matplotlib\axis.py", line 892, in iter_ticks    majorLocs = self.major.locator()  File "C:\WinPython-64bit-2.7.10.3\python-2.7.10.amd64\lib\site-packages\matplotlib\dates.py", line 1006, in __call__    self.refresh()  File "C:\WinPython-64bit-2.7.10.3\python-2.7.10.amd64\lib\site-packages\matplotlib\dates.py", line 1026, in refresh    dmin, dmax = self.viewlim_to_dt()  File "C:\WinPython-64bit-2.7.10.3\python-2.7.10.amd64\lib\site-packages\matplotlib\dates.py", line 770, in viewlim_to_dt    return num2date(vmin, self.tz), num2date(vmax, self.tz)  File "C:\WinPython-64bit-2.7.10.3\python-2.7.10.amd64\lib\site-packages\matplotlib\dates.py", line 419, in num2date    return _from_ordinalf(x, tz)  File "C:\WinPython-64bit-2.7.10.3\python-2.7.10.amd64\lib\site-packages\matplotlib\dates.py", line 271, in _from_ordinalf    dt = datetime.datetime.fromordinal(ix).replace(tzinfo=UTC)ValueError: ordinal must be >= 1