public static ZonedDateTime getDateTime() {
        return IMPLEMENTATION_DATE != null ? DateTimeUtils.zonedDateTimeOf(IMPLEMENTATION_DATE) : ZonedDateTime.now(Clock.systemUTC());
    }
Gets specification version from the manifest package.

@return the specification version
core/cas-server-core-util-api/src/main/java/org/apereo/cas/util/CasVersion.java