java.util.Date should call default[Read|Write]Object to strictly conform to the Serialization spec ( even though it does not have any persistent state, which it could conceivably do at some point in the future, but probably won't ).

diff --git a/src/java.base/share/classes/java/util/Date.java b/src/java.base/share/classes/java/util/Date.java
--- a/src/java.base/share/classes/java/util/Date.java
+++ b/src/java.base/share/classes/java/util/Date.java
@@ -1317,6 +1317,7 @@
    private void writeObject(ObjectOutputStream s)
         throws IOException
    {
+ s.defaultWriteObject();
        s.writeLong(getTimeImpl());
    }

@@ -1326,6 +1327,7 @@
    private void readObject(ObjectInputStream s)
         throws IOException, ClassNotFoundException
    {
+ s.defaultReadObject();
        fastTime = s.readLong();
    }