title: mac using date to show seconds has "illegal time format" error
body: <p>I tried the following on mac terminal, and found it has some problem:</p>
  
  <pre><code>date –j –f '%d-%b-%Y' "22-Aug-2013" "+%s"
  date: illegal time format
  usage: date [-jnu] [-d dst] [-r seconds] [-t west] [-v[+|-]val[ymwdHMS]] ... 
              [-f fmt date | [[[mm]dd]HH]MM[[cc]yy][.ss]] [+format]
  </code></pre>
  
  <p>Could anybody help me to parse this string <code>22-Aug-2013</code> and get the epoch seconds?</p>