Datetime formatting

Hello,
i have some problems formatting my plot with dates on the x-axis.

My time array contains datetime objects with year,month,day,hour,minute.
Matplotlib shows hour, minute, second and the timezone. I want only hour and
minute! I set my timezone in the matplotlibrc to 'UTC', but mpl shows still
CEST.

Here is a code snippet:

fig = figure(figsize=(8,7))
ax = fig.add_subplot(211)
xticks(visible=False)
ax.plot(...)
bx.twinx()
bx.plot(...)
cx = fig.add_subplot(211,sharex=ax)
cx.plot(...)
dx = cx.twinx()
dx.plot(...)

I tried:

from matplotlib.dates import DateFormatter
fmt = DateFormatter('%H:%M')
cx.xaxis.set_major_formatter(fmt)
and
ax.xaxis.set_major_formatter(fmt)

but this doesn't change anything!

I hope someone can help me.

Greeting

MQ