@Override
        public ZonedDateTime convert(
            @Nonnull final String source) {
            if (StringUtils.isBlank(source)) {
                return null;
            }
            return DateTimeUtils.zonedDateTimeOf(source);
        }
The type String to zoned date time converter.
support/cas-server-support-mongo-core/src/main/java/org/apereo/cas/mongo/BaseConverters.java