title: First day of the month from a POSIXct date time using lubridate
body: <p>Given a POSIXct date time, how do you extract the first day of the month for aggregation?</p>
  
  <pre><code>library(lubridate)
  
  full.date &lt;- ymd_hms("2013-01-01 00:00:21")
  </code></pre>