title: Find dates that fail to parse in R Lubridate
body: <p>As a R novice I'm pulling my hair out trying to debug cryptic R errors. I have csv that containing 150k lines that I load into a data frame named 'date'. I then use lubridate to convert this character column to datetimes in hopes of finding min/max date.</p>
  
  <pre><code>  dates &lt;- csv[c('datetime')]
    dates$datetime &lt;- ymd_hms(dates$datetime)
  </code></pre>
  
  <p>Running this code I receive the following error message:</p>
  
  <pre><code>Warning message:
  3 failed to parse. 
  </code></pre>
  
  <p>I accept this as the CSV could have some janky dates in there and next run:</p>
  
  <pre><code>min(dates$datetime) 
  max(dates$datetime)
  </code></pre>
  
  <p>Both of these return NA, which I assume is from the few broken dates still stored in the data frame. I've searched around for a quick fix, and have even tried to build a foreach loop to identify the problem dates, but no luck. What would be a simple way to identify the 3 broken dates?</p>
  
  <pre><code>example date format: 2015-06-17 17:10:16 +0000
  </code></pre>