--- old/src/java.base/share/classes/java/io/File.java	2017-05-22 13:15:56.000000000 -0700
+++ new/src/java.base/share/classes/java/io/File.java	2017-05-22 13:15:56.000000000 -0700
@@ -934,7 +934,9 @@
      *          (00:00:00 GMT, January 1, 1970), or <code>0L</code> if the
      *          file does not exist or if an I/O error occurs; the value may
      *          be negative in which case its absolute value indicates the
-     *          number of milliseconds before the epoch
+     *          number of milliseconds before the epoch; if the last-modified
+     *          time is the epoch, the value will be unity (<code>1</code>)
+     *          so as to avoid ambiguity with the case of a non-existent file
      *
      * @throws  SecurityException
      *          If a security manager exists and its {@link
@@ -949,7 +951,18 @@
         if (isInvalid()) {
             return 0L;
         }
-        return fs.getLastModifiedTime(this);
+        long lastModifiedTime = fs.getLastModifiedTime(this);
+
+        //
+        // In the infinitesimally probable event that the last-modified time
+        // of the file is the epoch (zero), return unity instead so as to avoid
+        // ambiguity with the case of a non-existent file which returns zero.
+        //
+        if (lastModifiedTime == 0) {
+            lastModifiedTime = 1;
+        }
+
+        return lastModifiedTime;
     }
 
     /**
--- /dev/null	2017-05-22 13:15:57.000000000 -0700
+++ new/test/java/io/File/FileTimeAtEpoch.java	2017-05-22 13:15:57.000000000 -0700
@@ -0,0 +1,59 @@
+/*
+ * Copyright (c) 2017, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * @test
+ * @bug 8180767
+ * @summary Ensure that lastModified() returns unity for files modified at epoch
+ */
+
+import java.io.File;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.attribute.FileTime;
+import java.util.concurrent.TimeUnit;
+
+public class FileTimeAtEpoch {
+    public static void main(String[] args) throws Throwable {
+        String dirname = System.getProperty("test.dir", ".");
+        System.out.format("Working directory: %s%n", dirname);
+        File dir = new File(dirname);
+        File file = File.createTempFile("epoch", ".txt");
+        System.out.format("Test file: %s%n", file.getAbsolutePath());
+        FileTime epoch = FileTime.from(0L, TimeUnit.MILLISECONDS);
+        Path path = file.toPath();
+        FileTime current = Files.getLastModifiedTime(path);
+        System.out.format("Current last-modified time: %s%n",
+            current.toString());
+        Files.setLastModifiedTime(path, epoch);
+        FileTime updated = Files.getLastModifiedTime(path);
+        System.out.format("Updated last-modified time: %s%n",
+            updated.toString());
+        long lastModified = file.lastModified();
+        if (lastModified != 1L) {
+            throw new RuntimeException
+                ("Expected last-modified time of 1 but obtained "
+                + lastModified);
+        }
+    }
+}