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matplotlib.axes.Axes.xaxis_date
Axes.xaxis_date(tz=None)- 
    
Sets up x-axis ticks and labels that treat the x data as dates.
tz is a timezone string or
tzinfoinstance. Defaults to rc value. 
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 http://matplotlib.org/2.0.2/api/_as_gen/matplotlib.axes.Axes.xaxis_date.html