import matplotlib.pyplot as plt
import pandas as pd
import matplotlib.dates as mdates
plt.scatter(pd.to_datetime(['10:00', '11:00', '12:00']), [30, 40, 50])
plt.axis(['9:00','13:00', None, None]) # or plt.xlim('9:00','13:00')
myFmt = mdates.DateFormatter('%H:%M')
plt.gca().xaxis.set_major_formatter(myFmt)
plt.show()