title: Convert modified julian date to UTC
body: <p>I have a large file with about 200000 lines and I'd like to get the file in a way that I can use the zoo package to plot the file and to truncate by date,month and time. The first column is the modified julian date and the second is temperature.</p>
  
  <p>I'd appreciate any help. 
  The file looks like:</p>
  
  <pre><code>4812663507.000000,1.76438
  4812663512.000000,1.65121
  4812663517.000000,1.60362
  4812663522.000000,1.51509
  </code></pre>