jodd-core/src/main/java/jodd/io/FileUtil.java
public static boolean isOlder(final File file, final File reference) {
		checkReferenceExists(reference);
		return isOlder(file, reference.lastModified());
	}
public static boolean isOlder(final File file, final File reference) {
		checkReferenceExists(reference);
		return isOlder(file, reference.lastModified());
	}
Uses {@link File#lastModified()} for reference.

@see #isOlder(File, long)