fix millisecond parsing errors (#895)

* fix millisecond parsing errors

* nits

Author: elharo

google-http-client/src/main/java/com/google/api/client/util/DateTime.java

@@ -273,7 +273,7 @@ public int hashCode() {
    *     exception is thrown if {@code str} doesn't match {@code RFC3339_REGEX} or if it contains a
    *     time zone shift but no time.
    */
-  public static DateTime parseRfc3339(String str) throws NumberFormatException {
+  public static DateTime parseRfc3339(String str) {
     return parseRfc3339WithNanoSeconds(str).toDateTime();
   }
 
@@ -285,9 +285,9 @@ public static DateTime parseRfc3339(String str) throws NumberFormatException {
    *     exception is thrown if {@code str} doesn't match {@code RFC3339_REGEX} or if it contains a
    *     time zone shift but no time.
    */
-  public static SecondsAndNanos parseRfc3339ToSecondsAndNanos(String str)
-      throws IllegalArgumentException {
-    return parseRfc3339WithNanoSeconds(str).toSecondsAndNanos();
+  public static SecondsAndNanos parseRfc3339ToSecondsAndNanos(String str) {
+    Rfc3339ParseResult time = parseRfc3339WithNanoSeconds(str);
+    return time.toSecondsAndNanos();
   }
 
   /** A timestamp represented as the number of seconds and nanoseconds since Epoch. */
@@ -335,7 +335,7 @@ public String toString() {
     }
   }
 
-  /** Result of parsing a Rfc3339 string. */
+  /** Result of parsing an RFC 3339 string. */
   private static class Rfc3339ParseResult implements Serializable {
     private final long seconds;
     private final int nanos;
@@ -400,6 +400,7 @@ private static Rfc3339ParseResult parseRfc3339WithNanoSeconds(String str)
       }
     }
     Calendar dateTime = new GregorianCalendar(GMT);
+    dateTime.clear();
     dateTime.set(year, month, day, hourOfDay, minute, second);
     long value = dateTime.getTimeInMillis();
 

google-http-client/src/test/java/com/google/api/client/util/DateTimeTest.java

@@ -28,12 +28,6 @@ public class DateTimeTest extends TestCase {
 
   private TimeZone originalTimeZone;
 
-  public DateTimeTest() {}
-
-  public DateTimeTest(String testName) {
-    super(testName);
-  }
-
   @Override
   protected void setUp() throws Exception {
     originalTimeZone = TimeZone.getDefault();
@@ -225,8 +219,18 @@ public void testParseRfc3339ToSecondsAndNanos() {
     assertParsedRfc3339(
         "2018-03-01T10:11:12.1000Z", SecondsAndNanos.ofSecondsAndNanos(1519899072L, 100000000));
   }
+  
+  public void testEpoch() {
+    assertParsedRfc3339(
+        "1970-01-01T00:00:00.000Z", SecondsAndNanos.ofSecondsAndNanos(0, 0));
+  }
+
+  public void testOneSecondBeforeEpoch() {
+    assertParsedRfc3339(
+        "1969-12-31T23:59:59.000Z", SecondsAndNanos.ofSecondsAndNanos(-1, 0));
+  }
 
-  private void assertParsedRfc3339(String input, SecondsAndNanos expected) {
+  private static void assertParsedRfc3339(String input, SecondsAndNanos expected) {
     SecondsAndNanos actual = DateTime.parseRfc3339ToSecondsAndNanos(input);
     assertEquals(
         "Seconds for " + input + " do not match", expected.getSeconds(), actual.getSeconds());
@@ -249,7 +253,7 @@ public void testParseAndFormatRfc3339() {
     assertEquals(expected, output);
   }
 
-  private void expectExceptionForParseRfc3339(String input) {
+  private static void expectExceptionForParseRfc3339(String input) {
     try {
       DateTime.parseRfc3339(input);
       fail("expected NumberFormatException");