code: @Deprecated
      public DateTime toDateTimeAtMidnight(DateTimeZone zone) {
          zone = DateTimeUtils.getZone(zone);
          Chronology chrono = getChronology().withZone(zone);
          return new DateTime(getYear(), getMonthOfYear(), getDayOfMonth(), 0, 0, 0, 0, chrono);
      }
docs: Converts this LocalDate to a full datetime at midnight using the
  specified time zone.
  <p>
  This method will throw an exception if the time zone switches
  to Daylight Savings Time at midnight and this LocalDate represents
  that switchover date. The problem is that there is no such time as
  midnight on the required date, and as such an exception is thrown.
  <p>
  This method uses the chronology from this instance plus the time zone
  specified.
  <p>
  This instance is immutable and unaffected by this method call.
  
  @param zone  the zone to use, null means default zone
  @return this date as a datetime at midnight
  @deprecated Use {@link #toDateTimeAtStartOfDay(DateTimeZone)} which won't throw an exception