As per "The Enemy of the World", Earth has formed a world government called the World Zone Authority by 2018. This system is indicated to have been in existence for some time, with the World Zone Authority also being seen to be based in the United Nations building in New York City. This is contradicted by all other stories set in the early 21st century. Among them is "The Power of Three", which indicates that the United Nations and national governments are in existence as late as 2020. Due to the nature of time travel later established in the program, it is possible that this story and the events leading up to this version of history took place in an alternate timeline.