Seconds value may be incorrect:
===== Here is the minimized test =====
import java.sql.Timestamp;
class java_sql_Timestamp1 {
  public static void main (String args[]) {
      Timestamp t=new Timestamp(-1800);
      System.out.println("t = " + t.toString());
      System.out.println("t = " + t.toGMTString()); //should print
                                       // "t = 31 Dec 1969 23:59:58 GMT"
      System.out.println("t.getTime() = " + t.getTime()); //should print
                                       // "-2000"
  }
}
===== Here is the output of the test =====
t = 1969-12-31 15:59:58.2
t = 31 Dec 1969 23:59:59 GMT
t.getTime() = -1001