title: Change the value of a date in a data frame in R
body: <p>I have a data frame called df which looks like this:</p>
  <pre><code>ID      DATE           RAIN
  79001   2013-11-28      2.0
  79001   2013-11-29      34.0
  79001   2013-11-30      3.0
  79002   2013-10-09      17.2
  79002   2013-10-10      5.0
  79002   2013-10-11      12.0
  79003   2013-10-14      14.8
  79003   2013-10-15      4.8
  79003   2013-10-16      0
  </code></pre>
  <p>There is a mistake in the data, such as that for ID 79001 the month is wrong, it should be September and not November. How can I fix the date from 2013-11-28 to 2013-09-28 ?.
  I tried the following:</p>
  <pre><code>df[df$DATUM == &quot;2013-11-28&quot;] &lt;- &quot;2013-09-28&quot;
  </code></pre>
  <p>This however doesn't seem like a good way and it doesn't work.
  I thought about converting the Date to a character and then changing the value, but I don't know if it works and if it works, how to do it</p>
  <p>I am thankful for any help</p>
  <p>Thank you a lot</p>