title: Ruby date parsing
body: <p>I'm sure I'm missing something obvious, but - I'm trying to parse a date like "8/5/2018" (in m/d/y format).  Ruby seems perfectly capable of creating dates in this format using the format string <code>%-m/%-d/%Y</code> and <code>strftime</code>, but for some reason <code>strptime</code> can't read it?</p>
  
  <pre><code>[1] pry(main)&gt; require 'date'
  =&gt; true
  [2] pry(main)&gt; format = '%-m/%-d/%Y'
  =&gt; "%-m/%-d/%Y"
  [3] pry(main)&gt; today = Date.today.strftime(format)
  =&gt; "8/5/2018"
  [4] pry(main)&gt; Date.strptime(today, format)
  ArgumentError: invalid date
  from (pry):4:in `strptime'
  </code></pre>
  
  <p>Does <code>strptime</code> use a different set of format keys than <code>strftime</code> (the ruby docs seem to suggest that they're the same)?  Or am I missing something else here?</p>