public Optional<Instant> getCreationTime() {
    if (creationTime != null) {
      return Optional.of(Instants.fromMillisOrIso8601(creationTime, "creationTime"));
    }
    return Optional.empty();
  }
Returns {@link Instant} representing creation time of container.

@return an optional creation time
jib-cli/src/main/java/com/google/cloud/tools/jib/cli/CommonContainerConfigCliOptions.java