Unfortunately, the review dates cannot be changed. They correspond to the date in which the review was left whether it was in the admin dashboard or on the website.
If you have past reviews from other customers, you could do an import of a CSV file with the correct date.
Or if you do not wish to show the dates, you can turn them off here: https://judge.me/settings?jump_to=review+timestamps
Can you please tell me if I can manually put the date which I want? I have put some reviews and the date is when I wrote the review. How can I change this?