title: Sort column with date and time in R dataframe
body: <p>I merged several other dataframes together. However, now the dates are no longer chronologically order (See photo). How do I order the dataframe based on the values of the 'Date' column?</p>
  <p><a href="https://i.stack.imgur.com/vB8IE.png" rel="nofollow noreferrer">R dataframe output which I want to change</a></p>
  <p>I first tried to set the 'Date' column as index, but since the 'Date' column does not only have unique values, I can't.</p>
  <p>Whenever I do:</p>
  <pre><code>new_df &lt;- new_df[order(new_df$Date),]
  </code></pre>
  <p>it only sorts the dates based on their first value.</p>
  <p>Next to that, sometimes there are multiple exact the same values for the 'Date' column. How can I make the index the same whenever the 'Date' column has the exact same value?</p>