title: bash shell date parsing, start with specific date and loop through each day in month
body: <p>I need to create a bash shell script starting with a day and then loop through each subsequent day formatting that output as %Y_%m_d</p>
  
  <p>I figure I can submit a start day and then another param for the number of days.</p>
  
  <p>My issue/question is how to set a DATE (that is not now) and then add a day.</p>
  
  <p>so my input would be 2010_04_01 6</p>
  
  <p>my output would be </p>
  
  <pre><code>2010_04_01
  2010_04_02
  2010_04_03
  2010_04_04
  2010_04_05
  2010_04_06
  </code></pre>