title: Regex in python seems to be not working with some hyphen
body: <p>I am trying to parse some dates with following regex. But it seems to be working with some hyphens only. Please have a look at the link below. It is not matching some dates. I added that particular hyphen, but it works only in rgex101.com. Not in Python.</p>
  
  <pre><code>((?:(?&lt;= )|^)((?:0?[1-9]|1[0-2])?[/-] ?(?:[12][0-9])?[0-9]{2})\b(?:[\s-]+)[/-]{0,2}\s*\b((?:0?[1-9]|1[0-2]) ?[/-] ?(?:[12][0-9])?[0-9]{2})\b)
  </code></pre>
  
  <p><a href="https://regex101.com/r/vI6qN1/1" rel="nofollow">https://regex101.com/r/vI6qN1/1</a></p>