What would be the best way to do a world wide "reset"?

Hey guys. I have a worldbuilding problem. So in my world each year is 20 earth years long. The new year starts with the change of season. So a new year will start around when winter, spring summer or fall begin. This alternate timeline is what I have come up with so far:<br><br>Old Calendar:<br><br>New Calendar:<br><br>1st day of Spring- 1st Day of Year 0 Freezing Point. Magic now exists on earth.<br><br>1st day of Summer- 1st Day of Year 1 Archipelago. First sighting of a dragon on earth.<br><br>1st day of Winter- 1st Day of Year 2 Industrial Archipelago. Industrial revolution, a lot of energy and resources consumed.<br><br>1st day of Spring- 1st Day of Year 3 War Freezing Point. Dragon Vs Humanity war, lots of new technology and magic developed and used.<br><br>1st day of Summer- 1st Day of Year 4 War Archipelago. Magic and technology trapped inside new alternate dimension, extremely powerful dragon drives humanity to brink of extinction, energy and resources consumed.<br><br>1st day of Winter- 1st Day of Year 5 Death Freezing Point. New powerful dragon drives humanity almost to extinction, even less energy consumed.<br><br>1st day of Summer- 1st Day of Year 6 Death Archipelago. The strongest dragon to have ever existed causes dragon evolution, extremely powerful dragons drive humanity to brink of extinction, even less energy consumed.<br><br>1st day of Winter- 1st Day of Year 7 Dark Freezing Point. Dragon causes global catastrophe and almost new ice age, with only a couple hundred humans left.<br><br>Now I want to make it so that this kind of thing never happens again, as it is crucial to this world. Somehow, humanity now has to make sure that this does not happen again. People knew that there were new alternate dimension because of the magic and technology trapped inside them. They decided to do "The Great Migration" which was a lot of time and effort to put all the humans on earth into these alternate dimensions, but when they did, they left behind on earth all the magic and technology. Some alternate dimensions with humans had magic but not technology, some had no magic and technology, and some had both. Humanity left behind on earth all the dragons and other creatures that were on earth. People knew that had they taken those dragons with them, that eventually they would reach Freezing Point again because there evolution would cause them to bring on Freezing Point. So they decided to trapped the dragons on earth, along with the magic and technology.<br><br>So the humans who had tech and magic were able to control the alternate dimensions and create a lot of new ones so that everyone could have there own world without magic and tech. So people could live without the fear of dragons and other monsters trapped on earth with them. So in the end everyone is happy living in their own worlds without magic and tech and are no longer trapped on a "time bomb" of a earth with an almost inevitable Freezing Point.