title: Transform "ambigous" factor to Posixct value
body: <p>this is an extract with some dates.</p>
  
  <pre><code>df&lt;-structure(c(2L, 3L, 1L, 4L, 5L), .Label = c("05JUL2014:00:00:00", 
  "07FEB2014:00:00:00", "10JUL2012:00:00:00", "19APR1998:00:00:00", 
  "22DEC2010:00:00:00"), class = "factor")
  </code></pre>
  
  <p>I would like to transform this as Date or Posixct.</p>
  
  <p>I Tried this :</p>
  
  <pre><code>as.POSIXct(df,"%d%b%Y:%H:%M:%S")
  </code></pre>
  
  <p>but it dont seems to be the good solution. can anyone show me my mistake ?</p>
  
  <p>edit : i also tried this:</p>
  
  <pre><code>as.POSIXct(df, format = "%d%b%Y:%H:%M:%S")
  </code></pre>
  
  <p>but I obtain</p>
  
  <pre><code>NA NA NA NA
  </code></pre>
  
  <p>Re edit :</p>
  
  <pre><code>as.POSIXct("07FEB2014:00:00:00", format = "%d%b%Y:%H:%M:%S")
  </code></pre>
  
  <p>return</p>
  
  <pre><code>NA
  </code></pre>
  
  <p>but</p>
  
  <pre><code>as.POSIXct("072014:00:00:00", format = "%d%Y:%H:%M:%S")
  </code></pre>
  
  <p>return</p>
  
  <pre><code>"2014-09-07 CEST"
  </code></pre>
  
  <p>%b dont seems to understand "FEB" , my computer use "french" Locale... (but it also dont seems to understand FEV or JAN (instead of FEB and JAN)</p>
  
  <p>Final? edit</p>
  
  <p>I found a solution by using this function :   </p>
  
  <pre><code> Sys.setlocale("LC_TIME", "C")
  </code></pre>
  
  <p>I dont realy understand why, but it's seems to be ok.</p>
  
  <p>thks</p>