The article explores how our preferences for time affect fairness between different generations. By using a model with different generations, uncertain lifetimes, population growth, and technological advancements, the study sets limits on how much we should discount the future. It shows that there are certain discount rates that are best for society, and these can lead to either plans that favor older generations or plans that prioritize the future. The paper also corrects some mistakes made in a previous study on the same topic.