title: strtotime returns current year when input is in the format of YYYY and the value is greater then 1999
body: <p>I'm not sure that this is a bug since after searching I can't find any duplicate experiences- however, this one has me stumped.</p>
  
  <p>While in the midst of a (rather painful) script that is intended to take a bunch of freetext records and convert them to useful date records, my trusty friend strtotime() seems to have let me down.</p>
  
  <p>For testing purposes, I boiled the code down to this:</p>
  
  <pre><code>&lt;?=date('Y', strtotime("1999"));?&gt;
  </code></pre>
  
  <p>Output shows: 1999</p>
  
  <pre><code>&lt;?=date('Y', strtotime("1981"));?&gt;
  </code></pre>
  
  <p>Output shows: 1981</p>
  
  <pre><code>&lt;?=date('Y', strtotime("2001"));?&gt;
  </code></pre>
  
  <p>Output shows: 2012</p>
  
  <pre><code>&lt;?=date('Y', strtotime("2021"));?&gt;
  </code></pre>
  
  <p>Output shows: 2012</p>
  
  <p>Everything seems fine until the input exceeds "1999"- From that point on, every year before and after the current one returns the current year (2012)</p>
  
  <p>Any input is much appreciated.</p>