How to add string tick labels to 2D plots?

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Is there a way to access ticks labels to rotate them? I've tried Graphics.matplotlib() and set_rotation(), but this doesn't seem to produce changes. Am I doing wrong things?

# Z is a list of [(x1,y1),(x2,y2)...]
# x1,x2 are dates
# The formatter and locator are working correctly, but the problem is all labels are oriented horizontally, messing all together. Need to rotate them
p = list_plot( Z, ticks=[10, None], tick_formatter=[dates.DateFormatter('%d.%m.%Y'), None], axes_labels=[ 'Days', '$\\log \\;{N}$' ], scale='semilogy' )

G = p.matplotlib()
labels = G.axes[0].xaxis.get_ticklabels()
labels = list(labels)

for label in labels:
    label.set_rotation(45)