Millenarianism (also millenarism), from Latin mīllēnārius "containing a thousand", is the belief by a religious, social, or political group or movement in a coming major transformation of society, after which all things will be changed. Millenarianism is a concept or theme that exists in many cultures and religions.

Millennialism

Millennialism is a specific type of Christian millenarianism, and is sometimes referred to as "chiliasm" from the New Testament use of the Greek chilia (thousand). It is part of the broader form of apocalyptic expectation. A core doctrine in some variations of Christian eschatology is the expectation of the Second Coming and the establishment of a Kingdom of God on Earth. According to an interpretation of prophecies in the Book of Revelation, this Kingdom of God on Earth will last a thousand years or more (a millennium).

The application of an apocalyptic timetable to the establishment or changing of the world has happened in many cultures and religions, and continues to this day, and is not relegated to the sects of major world religions.

The 2012 phenomenon was a range of eschatological beliefs that cataclysmic or otherwise transformative events would occur on or around 21 December 2012. This date was regarded as the end-date of a 5,126-year-long cycle in the Mesoamerican Long Count calendar, and as such, festivities to commemorate the date took place on 21 December 2012 in the countries that were part of the Mayan civilization (Mexico, Guatemala, Honduras, and El Salvador), with main events at Chichén Itzá in Mexico, and Tikal in Guatemala.

Various astronomical alignments and numerological formulae were proposed as pertaining to this date. A New Age interpretation held that the date marked the start of a period during which Earth and its inhabitants would undergo a positive physical or spiritual transformation, and that 21 December 2012 would mark the beginning of a new era. Others suggested that the date marked the end of the world or a similar catastrophe. Scenarios suggested for the end of the world included the arrival of the next solar maximum, an interaction between Earth and the black hole at the center of the galaxy, or Earth's collision with a planet called Nibiru.