Can’t mock LocalDateTime. now() in nested calls using PowerMockito

I want to mock the update method and I want to check if it returns false in validate method when the time is false. so I tried mocking call to method. It works if I directly call timeValidator.validate() but when I call service.update() it gives a new object of LocalDateTime, maybe because it is nested in 3 levels it is not passing the mocked object.

The string to TimeValidator constructor is like “20:00”.
So what this program is supposed to do is if I the activity is to eat and for that time limit is “22:00” then it validator should return false if the current time is after 10 PM.
Sample code is like below:

public class ServiceImpl{
    //all other methods    
    public void update(){
      //other code
      List<Validator> validators = new ArrayList<>();
      validators.add(new TimeValidator(timeString);
      //other validators
      Activity activity = new Activity(userId, validators);

//Activity Class
public class Activity{

    //other methods

       public void execute(){
           for(v : validators){
                   throw MyException();

//TimeValidator class
TimeValidator implements Validator{
    public TimeValidator(String timeString){
        //some code
    public boolean validate(){
        LocalDateTime currentTime =;
        LocalDateTime cutOffTime = LocalDateTime.of(, LocalDateTime.parse(timeString));
        return currentTime.isBefore(cutOffTime);

//Test class
public TestClass{

    @Test(expected = MyException.class)
    public void testUpdate(){
        //other code to get real object of service

        LocalDateTime currentTime = LocalDateTime.of(2018,01,02,22,15);