code: public DateTimeStamp setDateTimeStamp(Date dateTimeStamp) {
  		DateTimeStamp prop = (dateTimeStamp == null) ? null : new DateTimeStamp(dateTimeStamp);
  		setDateTimeStamp(prop);
  		return prop;
  	}
docs: Sets either (a) the creation date of the iCalendar object (if the
  {@link Method} property is defined) or (b) the date that the journal
  entry was last modified (the {@link LastModified} property also holds
  this information). This journal entry object comes populated with a
  {@link DateTimeStamp} property that is set to the current time. This is a
  <b>required</b> property.
  @param dateTimeStamp the date time stamp or null to remove
  @return the property that was created
  @see <a href="http://tools.ietf.org/html/rfc5545#page-137">RFC 5545
  p.137-8</a>
  @see <a href="http://tools.ietf.org/html/rfc2445#page-130">RFC 2445
  p.130-1</a>