Religion of Buddhism for the 21st Century

This is an outline of modern Buddhist thought, adding 21st Century knowledge to what we have gleaned from scriptural writings and science since the time of Buddha. Buddhism is one of the world's largest religions, yet the different groups range from idol worshipers to atheists. Siddhartha Gautama the Buddha lived in a society where people were mostly atheists or traditional polytheists accustomed to stories of many gods.
There is little mention of One Supreme Being in Buddha's teachings because no one at that time would have listened. Your beliefs do not make you a free thinker; what makes you a free thinker is the ability to change your beliefs based on new information. Topics like the Underworld and Enlightenment are spiritual matters of great importance to mankind, so it is time to redefine the Religion of Buddhism considering new information that has come to light in the 21st Century.
There are four Ages in ancient writings: this is the Final Age, so all people should be prepared for the Afterlife with knowledge of exactly how life works and what is required to succeed in reaching the reward of eternity.