title: Subtracting pandas Dataframe values from today's date
body: <p>I have a dataframe that looks like this:</p>
  
  <pre><code>Name  A    B    C
  D1    1    3    3
  D2    2    4    4
  D3    2    1    1
  </code></pre>
  
  <p>How can I create a new dataframe of the same size where every value is today's date minus the value of my first dataframe? </p>
  
  <p>for example, if today is 2018-04-27, my new dataframe would look like this:</p>
  
  <pre><code>Name  A             B             C  
  D1    2018-04-26    2018-04-24    2018-04-24
  D2    2018-04-25    2018-04-23    2018-04-23
  D3    2018-04-25    2018-04-26    2018-04-26
  </code></pre>
  
  <p>I'm thinking the solution will include something like </p>
  
  <pre><code>df2.iloc[1,1] = datetime.today() - timedelta(days=df1[1,1])
  </code></pre>
  
  <p>but I'm running into all kinds of type errors and problems looping through the original df</p>