private String getRuleAge(final Map<Instant, Set<DataRetentionRule>> earliestRetainedCreationTimeMap,
                              final Instant createTime) {
        final Set<DataRetentionRule> rules = earliestRetainedCreationTimeMap.get(createTime);
        if (rules == null) {
            return null;
        } else if (rules.isEmpty()) {
            return DataRetentionRule.FOREVER;
        } else {
            return rules.iterator()
                    .next()
                    .getAgeString();
        }
    }
Pkg private so we can test with a known now time
stroom-data/stroom-data-retention-impl/src/main/java/stroom/data/retention/impl/DataRetentionPolicyExecutor.java