How to unit test a method involving time factor/

I have the following piece of code which has time factor in it. I have trouble thinking how to do unit test for this piece of code.

public void someMethod(MultipartFile file,String username){
long timeNow = System.currentTimeMillis();
        byte[] bytes = file.getBytes();
        String fileLocation = defaultLocation +username+"_picture_"+timeNow+"_"+file.getOriginalFilename();
        Path path = Paths.get(fileLocation);
        Files.write(path, bytes);
}

Since there is time involved i am unable to do unit testing. Can anyone please help in this? I use Mockito for unit testing btw