title: Date/Time not plotting as expected
body: <p>I'm going to be plotting some temperature data over time and wrote a test program to see with Matplotlib can do for me.  When I plot the the date the date time does not display as I would expect, the date is output but the time is some type of counter not the time of day as expected.</p>
  
  <p>Sample data:</p>
  
  <pre class="lang-py prettyprint-override"><code>import pandas as pd
  
  df = pd.DataFrame([
      ['08/16/2019 00:00:00',70 ],['08/17/2019 00:05:00',70.5 ],
      ['08/17/2019 00:10:00',70.5],['08/17/2019 00:15:00',71 ],
      ['08/17/2019 00:20:00',72 ],['08/17/2019 00:25:00',73 ],
      ['08/17/2019 00:30:00',74 ],['08/17/2019 00:35:00',74.5], 
      ['08/17/2019 00:40:00',75 ],['08/17/2019 00:45:00',74.5], 
      ['08/17/2019 00:50:00',73 ],['08/17/2019 00:55:00',75 ],
      ['08/17/2019 01:00:00',72.5],['08/17/2019 01:05:00',78 ],
      ['08/17/2019 01:10:00',78]], columns=['Date Time', 'Temperature'])
  
  df
  Out[1]: 
                Date Time  Temperature
  0   08/16/2019 00:00:00         70.0
  1   08/17/2019 00:05:00         70.5
  2   08/17/2019 00:10:00         70.5
  3   08/17/2019 00:15:00         71.0
  4   08/17/2019 00:20:00         72.0
  5   08/17/2019 00:25:00         73.0
  6   08/17/2019 00:30:00         74.0
  7   08/17/2019 00:35:00         74.5
  8   08/17/2019 00:40:00         75.0
  9   08/17/2019 00:45:00         74.5
  10  08/17/2019 00:50:00         73.0
  11  08/17/2019 00:55:00         75.0
  12  08/17/2019 01:00:00         72.5
  13  08/17/2019 01:05:00         78.0
  14  08/17/2019 01:10:00         78.0
  </code></pre>
  
  <pre><code>import csv
  import matplotlib.pyplot as plt
  import numpy as np
  from datetime import datetime
  
  path="/home/mikejs/PythonSandbox/temps.csv"
  file = open(path,newline='')
  reader = csv.reader(file)
  header = next(reader)
  dates = []
  temps  = []
  
  for row in reader:
      date = datetime.strptime(row[0],'%m/%d/%Y %H:%M:%S')
      dates.append(date)
      temps.append(float(row[1]))
  
  plt.title("Temperatures Over Time")
  plt.plot(dates,temps )
  plt.ylabel('Temperatues')
  plt.xlabel('Date/Time')
  plt.xticks(rotation='45')
  plt.tight_layout();
  plt.savefig('temps.png')
  plt.show()
  </code></pre>
  
  <p><a href="https://i.stack.imgur.com/9OAjE.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/9OAjE.png" alt="enter image description here"></a></p>