Bug report

I wouldn't have expected to see the 29th of some of the month labelled
Bug summary
I wouldn't have expected to see the 29th of some of the month labelled

Code for reproduction

# Paste your code here
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import pandas as pd
import matplotlib.pyplot as plt
x = pd.date_range(start='1/1/2018', periods=80) # 80 days
y = pd.np.random.random(80)
plt.plot(x, y ,'o')
plt.xticks(rotation='vertical')

Actual outcome

# If applicable, paste the console output here
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Expected outcome

Matplotlib version

• Operating system: Win10 64bit
• Matplotlib version: 3.0.1
• Matplotlib backend (print(matplotlib.get_backend())): module://ipykernel.pylab.backend_inline
• Python version: 3.7.1
• Jupyter version (if applicable): 5.7.2
• Other libraries: pandas 0.23.4
• conda 4.5.11