Fix Timestamps.fromDate to correctly handle java.sql.Timestamps before unix epoch.

java/util/src/main/java/com/google/protobuf/util/Timestamps.java

@@ -343,7 +343,8 @@ public final class Timestamps {
   public static Timestamp fromDate(Date date) {
     if (date instanceof java.sql.Timestamp) {
       java.sql.Timestamp sqlTimestamp = (java.sql.Timestamp) date;
-      long integralSeconds = sqlTimestamp.getTime() / 1000L; // truncate the fractional seconds
+      long time = sqlTimestamp.getTime();
+      long integralSeconds = (time < 0) ? time / 1000L - 1 : time / 1000L ; // truncate the fractional seconds
       return Timestamp.newBuilder()
           .setSeconds(integralSeconds)
           .setNanos(sqlTimestamp.getNanos())

java/util/src/test/java/com/google/protobuf/util/TimestampsTest.java

@@ -475,6 +475,13 @@ public class TimestampsTest {
     Timestamp timestamp = Timestamps.fromDate(date);
     assertThat(Timestamps.toString(timestamp)).isEqualTo("1970-01-01T00:00:01.111Z");
   }
+  
+  @Test
+  public void testFromSqlTimestamp_beforeEpoch() {
+    Date date = new java.sql.Timestamp(-1111);
+    Timestamp timestamp = Timestamps.fromDate(date);
+    assertThat(Timestamps.toString(timestamp)).isEqualTo("1969-12-31T23:59:58.889Z");
+  }
 
   @Test
   public void testTimeOperations() throws Exception {