title: JodaTime equivalent of DateUtils.truncate()
body: <p>I have never used <a href="http://www.joda.org/joda-time/" rel="noreferrer">JodaTime</a> before, but answering this question, <a href="https://stackoverflow.com/questions/4131558/how-to-get-weekdays-in-a-month/4132083#4132083">How to get ordinal Weekdays in a Month</a>. </p>
  
  <p>I tried it and came up with this ugly code to unset all fields below day:</p>
  
  <pre><code>DateTime startOfMonth =
      input.withDayOfMonth(1)
          .withHourOfDay(0)       // there
          .withMinuteOfHour(0)    // has got to
          .withSecondOfMinute(0)  // be a shorter way
          .withMillisOfSecond(0); // to do this
  </code></pre>
  
  <p>Where the <a href="http://commons.apache.org/lang" rel="noreferrer">Commons / Lang</a> equivalent using <a href="http://commons.apache.org/lang/api-2.5/org/apache/commons/lang/time/DateUtils.html" rel="noreferrer">DateUtils</a> would be</p>
  
  <pre><code>Date startOfMonth = DateUtils.truncate(input, Calendar.MONTH);
  </code></pre>
  
  <p>What's the preferred idiom to do that in JodaTime?</p>