public static long getLowestTimestamp(Collection<HStoreFile> candidates) throws IOException {
    long minTs = Long.MAX_VALUE;
    for (HStoreFile storeFile : candidates) {
      minTs = Math.min(minTs, storeFile.getModificationTimestamp());
    }
    return minTs;
  }
Gets lowest timestamp from candidate StoreFiles
hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/StoreUtils.java