[core] fix nanoseconds handling for Timestamps (#1020)

Extracted from #1008, credit goes to @rdubya

Author: dr-itz

src/java/arjdbc/util/DateTimeUtils.java

@@ -217,9 +217,11 @@ public static RubyTime newDummyTime(final ThreadContext context, final Timestamp
         final int hours = time.getHours();
         final int minutes = time.getMinutes();
         final int seconds = time.getSeconds();
-        final int nanos = time.getNanos(); // max 999-999-999
+        int nanos = time.getNanos(); // max 999-999-999
+        final int millis = nanos / 1000000;
+        nanos = nanos % 1000000;
 
-        DateTime dateTime = new DateTime(2000, 1, 1, hours, minutes, seconds, defaultZone);
+        DateTime dateTime = new DateTime(2000, 1, 1, hours, minutes, seconds, millis, defaultZone);
         return RubyTime.newTime(context.runtime, dateTime, nanos);
     }
 
@@ -232,9 +234,11 @@ public static RubyTime newTime(final ThreadContext context, final Timestamp time
         final int hours = timestamp.getHours();
         final int minutes = timestamp.getMinutes();
         final int seconds = timestamp.getSeconds();
-        final int nanos = timestamp.getNanos(); // max 999-999-999
+        int nanos = timestamp.getNanos(); // max 999-999-999
+        final int millis = nanos / 1000000;
+        nanos = nanos % 1000000;
 
-        DateTime dateTime = new DateTime(year, month, day, hours, minutes, seconds, 0, defaultZone);
+        DateTime dateTime = new DateTime(year, month, day, hours, minutes, seconds, millis, defaultZone);
         return RubyTime.newTime(context.runtime, dateTime, nanos);
     }