title: Python - parse_dates=True adds vertical lines to my graph
body: <p>This is the first question I've posted here - so do let me know if I'm missing any structural etiquette or key information.</p>
  
  <p>I'm having an issue when plotting data from my CSV file - it seems that when I choose to "parse dates" (using parse_dates=True within my pd.read_csv function) my graph becomes an awful lot more jumpy than it should look.</p>
  
  <p>I've attached my code below showing when I do and don't parse dates - could someone point out what might be happening here and the best way to fix this?</p>
  
  <pre><code>sp500 = pd.read_csv("^GSPC.csv", index_col="Date", parse_dates=True)
  sp500["Adj Close"].plot()
  </code></pre>
  
  <p><img src="https://i.stack.imgur.com/J0f8H.png" alt="Result when parsing dates"></p>
  
  <pre><code>sp500 = pd.read_csv("^GSPC.csv", index_col="Date", parse_dates=False)
  sp500["Adj Close"].plot()
  </code></pre>
  
  <p><img src="https://i.stack.imgur.com/6LGXI.png" alt="Result when not parsing dates"></p>
  
  <p><strong>Edit:</strong> in case it's useful, the csv file is a download from the following link (I would post the csv file, though I haven't set myself up on a file hosting site yet):
  <a href="https://finance.yahoo.com/quote/%5EGSPC/history/" rel="nofollow noreferrer">S&amp;p 500 daily data</a></p>