public long normalizeToMillis(long secondsOrMillis) {
    if (isExpiryUnitSeconds()) {
      return TimeUnit.SECONDS.toMillis(secondsOrMillis);
    }
    return secondsOrMillis;
  }
Return the given timestamp as milliseconds.
If the given secondsOrMillis is already millis then no conversion is needed.
geode-core/src/main/java/org/apache/geode/internal/cache/ExpiryTask.java