Instant getBaseTime() {
        if (baseTime == null) {
            baseTime = NullSafe.getOrElseGet(
                    metaHolder,
                    MetaHolder::getMeta,
                    Meta::getCreateMs,
                    Instant::ofEpochMilli,
                    Instant::now);
        }
        return baseTime;
    }
Parsing dates that use week fields has to be done differently as week based parsing does not seem to
cope with conflicting default values for fields.
stroom-pipeline/src/main/java/stroom/pipeline/xsltfunctions/ParseDateTime.java