public static boolean isExpired(final X509CRL crl) {
        return isExpired(crl, ZonedDateTime.now(ZoneOffset.UTC));
    }
Determines whether the given CRL is expired by examining the nextUpdate field.

@param crl CRL to examine.
@return True if current system time is after CRL next update, false otherwise.
core/cas-server-core-util-api/src/main/java/org/apereo/cas/util/crypto/CertUtils.java