Nobody knows. Be assured it iswritten, Jesus said He would come back - so He will. What Jesus says you can trust?
At that time everything will be changed. Wickedness will be shown up and punished, all evil will be judged, the earth will be 'cleansed'' (cleaned up) and judgement day will happen too.
There will be a "New heaven and earth" with Jesus reigning as King and God (Revelations 21:1). "I will make all things new."
I am looking forward to that. It may not happen in my lifetime, but it could, today. Evil seems to flourish, wars seem to happen all the time. Also water is short and how do 7 or 8 billion people on earth manage? I find it hard to imagine.
Make sure you are on Jesus team!
Finally, my opinion: "How long will God permit one billion people to be too well fed and fat while 25,000 children die every day from easily preventable sickness and one billion go to bed hungry?"