title: Is there a way to check if a column is a Date in R?
body: <p>This is a pseudo followup to this question: <a href="https://stackoverflow.com/questions/18169762/why-is-ggplot-graphing-null-percentage-data-points">Why is ggplot graphing null percentage data points?</a></p>
  
  <p>Let's say this is my dataset:</p>
  
  <pre><code>Date        AE      AA      AEF     Percent
  1/1/2012    1211    1000    3556    0.03
  1/2/2012    100     2000    3221    0.43
  1/3/2012    3423    10000   2343    0.54
  1/4/2012    10000   3000    332     0.43
  1/5/2012    2342    500     4435    0.43
  1/6/2012    2342    800     2342    0.23
  1/7/2012    2342    1500    1231    0.12
  1/8/2012    111     2300    333 
  1/9/2012    1231    1313    3433    
  1/10/2012   3453    5654    222 
  1/11/2012   3453    3453    454 
  1/12/2012   5654    7685    3452 
  
  &gt; str(data)
  'data.frame':   12 obs. of  5 variables:
   $ Date   : Factor w/ 12 levels "10/11/2012","10/12/2012",..: 1 2 3 4 5 6 7 8 9 10 ...
   $ AE     : int  1211 100 3423 10000 2342 2342 2342 111 1231 3453 ...
   $ AA     : int  1000 2000 10000 3000 500 800 1500 2300 1313 5654 ...
   $ AEF    : int  3556 3221 2343 332 4435 2342 1231 333 3433 222 ...
   $ Percent: num  0.03 0.43 0.54 0.43 0.43 0.23 0.12 NA NA NA ...
  </code></pre>
  
  <p>I need something to tell that the 'Date' column is a Date type as opposed to a numeric or character type (this is because I have to convert the 'Date' column of the data input into an actual Date with as.Date(), ASSSUMING that I do not know the column names of the data set).</p>
  
  <pre><code>is.numeric(data[[1]]) returns False
  is.character(data[[1]]) returns False
  </code></pre>
  
  <p>I made the 'Date' column in Excel, formatting the column in the 'Date' format, then saved the file as a csv. What type is this in R? I seek an expression similar to the above that returns TRUE.</p>