title: Bash date command invalid date
body: <p>In linux bash when I enter <code>date -d "1986-01-01"</code> it shows error</p>
  
  <pre>
  date: invalid date "1986-01-01"
  </pre>
  
  <p>when <code>date -d "1986-01-02"</code> it works</p>
  
  <p>when <code>date -d "1987-01-01"</code> it also works</p>
  
  <p>Why <code>date -d "1986-01-01"</code> shows error in Linux Bash shell.</p>
  
  <p>I am using Fedora 16</p>