title: Delete directory based on date
body: <p>I am writing zsh script in which I have to get the date of 90th previous day from current date i.e I have to subtract 90 days from current date. Then I have to check the folders which have different dates as their names. I have to compare the directory date with the subtracted date and if the result is greater than the subtracted date, I have to delete the directory. </p>
  
  <p>For example:</p>
  
  <p>Let us say the current_date = 20131130 (yyyymmdd)</p>
  
  <p>subtracted_date=current_date - 90 days</p>
  
  <p>lets say there is a folder 20130621</p>
  
  <p>Now this folder name should be compare with the subtracted date. If greater than subtracted_date then i have to delete the directory.</p>