is.na() counts a valid date as NA : <p>I created a datetime column from a character column like this:</p>

<pre><code>dat$created_datetime &lt;- strptime(dat$created_at, format = '%d/%m/%Y %H:%M')
</code></pre>

<p>My cleanup code is reporting NAs in this column, but the entries look fine:</p>

<pre><code>&gt; dat$created_datetime[514]
[1] "2016-10-02 02:26:00"
&gt; is.na(dat$created_datetime[514])
[1] TRUE
&gt; str(dat$created_datetime)
POSIXlt[1:300400], format: "2016-06-29 13:10:00" "2016-06-30 03:56:00" "2016-07-05 09:43:00" "2016-07-12 06:47:00" "2016-07-13 06:57:00" "2016-07-13 10:11:00" ...
</code></pre>

<p>Only 62 of 300k rows are affected. I can't figure out what's going on.</p>
