/**
     * Sets the dateAndTime criterion. The specified date must be
     * equal to or later than the value of the thisUpdate component
     * of the <code>X509CRL</code> and earlier than the value of the
     * nextUpdate component. There is no match if the <code>X509CRL</code>
     * does not contain a nextUpdate component.
     * If <code>null</code>, no dateAndTime check will be done.
     * <p>
     * Note that the <code>Date</code> supplied here is cloned to protect
     * against subsequent modifications.
     *
     * @param dateAndTime the <code>Date</code> to match against
     *                    (or <code>null</code>)
     * @see #getDateAndTime
     */
    public void setDateAndTime(Date dateAndTime) {
        if (dateAndTime == null)
            this.dateAndTime = null;
        else
            this.dateAndTime = new Date(dateAndTime.getTime());
        this.skew = 0;
    } 

/* match on dateAndTime */
        if (dateAndTime != null) {
            Date crlThisUpdate = xcrl.getThisUpdate();
            Date nextUpdate = xcrl.getNextUpdate();
            if (nextUpdate == null) {
                if (debug != null) {
                    debug.println("X509CRLSelector.match: nextUpdate null");
                }
                return false;
            }
            Date nowPlusSkew = dateAndTime;
            Date nowMinusSkew = dateAndTime;
            if (skew > 0) {
                nowPlusSkew = new Date(dateAndTime.getTime() + skew);
                nowMinusSkew = new Date(dateAndTime.getTime() - skew);
            }
            if (nowMinusSkew.after(nextUpdate)
                || nowPlusSkew.before(crlThisUpdate)) {
                if (debug != null) {
                    debug.println("X509CRLSelector.match: update out of range");
                }
                return false;
            }
        }