The word arises from the Greek ? eschatos meaning "last" and -logy meaning "the study of", and first appeared in English around 1844. The Oxford English Dictionary defines eschatology as "the part of theology concerned with death, judgment, and the final destiny of the soul and of humankind".
In the context of mysticism, the term refers metaphorically to the end of ordinary reality and to reunion with the Divine. Many[quantify]religions treat eschatology as a future event prophesied in sacred texts or in folklore.
History is often divided[by whom?] into "ages" (aeons), which are time periods each with certain commonalities. One age comes to an end and a new age or world to come, where different realities are present, begins. When such transitions from one age to another are the subject of eschatological discussion, the phrase, "end of the world", is replaced by "end of the age", "end of an era", or "end of life as we know it". Much apocalyptic fiction does not deal with the "end of time" but rather with the end of a certain period, the end of life as it is now, and the beginning of a new period. It is usually a crisis that brings an end to current reality and ushers in a new way of living, thinking, or being. This crisis may take the form of the intervention of a deity in history, a war, a change in the environment, or the reaching of a new level of consciousness.
Most[quantify] modern eschatology and apocalypticism, both religious and secular, involve the violent disruption or destruction of the world; whereas Christian and Jewish eschatologies view the end times as the consummation or perfection of God's creation of the world, albeit with violent overtures, such as the Great Tribulation. For example, according to some ancient Hebrew worldviews, reality unfolds along a linear path (or rather, a spiral path, with cyclical components that nonetheless have a linear trajectory); the world began with God and is ultimately headed toward God's final goal for creation, the world to come.
Eschatologies vary as to their degree of optimism or pessimism about the future. In some eschatologies, conditions are better for some and worse for others, e.g. "heaven and hell". They also vary as to time frames. Groups claiming imminent eschatology are also referred to as Doomsday cults.
In Bahá'í belief, creation has neither a beginning nor an end. Instead, the eschatology of other religions is viewed as symbolic. In Bahá'í belief, human time is marked by a series of progressive revelations in which successive messengers or prophets come from God. The coming of each of these messengers is seen as the day of judgment to the adherents of the previous religion, who may choose to accept the new messenger and enter the "heaven" of belief, or denounce the new messenger and enter the "hell" of denial. In this view, the terms "heaven" and "hell" are seen as symbolic terms for the person's spiritual progress and their nearness to or distance from God. In Bahá'í belief, the coming of Bahá'u'lláh, the founder of the Bahá'í Faith, signals the fulfilment of previous eschatological expectations of Islam, Christianity and other major religions.
Christian eschatology is the study concerned with the ultimate destiny of the individual soul and the entire created order, based primarily upon biblical texts within the Old and New Testament.
Christian eschatology looks to study and discuss matters such as death and the afterlife, Heaven and Hell, the Second Coming of Jesus, the resurrection of the dead, the Rapture, the Tribulation, Millennialism, the end of the world, the Last Judgment, and the New Heaven and New Earth in the world to come.
Eschatological passages are found in many places in the Bible, both in the Old and the New Testaments. In the Old Testament, apocalyptic eschatology can be found notably in Isaiah 24-27, Isaiah 56-66, Joel, Zechariah 9-14 as well as closing chapters of Daniel, and Ezekiel. In the New Testament, applicable passages include Matthew 24, Mark 13, the parable of "The Sheep and the Goats" and in the Book of Revelation--although Revelation often occupies a central place in Christian eschatology.
The Second Coming of Christ is the central event in Christian eschatology within the broader context of the fullness of the Kingdom of God. Most Christians believe that death and suffering will continue to exist until Christ's return. There are, however, various views concerning the order and significance of other eschatological events.
The Book of Revelation is at the core of Christian eschatology. The study of Revelation is usually divided into four interpretative methodologies or hermeneutics. In the Futurist approach, Revelation is treated mostly as unfulfilled prophecy taking place in some yet undetermined future. In the Preterist approach, Revelation is chiefly interpreted as having prophetic fulfillment in the past. , principally, the events of the first century CE.
In the Historicist approach, Revelation provides a broad view of history, and passages in Revelation are identified with major historical people and events. This is view the Jewish scholars held, along with the early Christian church, and it was prevalent in Wycliffe's writings, and other Reformers such as Martin Luther,  John Calvin,  John Wesley,  and Sir Isaac Newton,  and many others.
In the Idealist approach, the events of Revelation are neither past nor future, but are purely symbolic, dealing with the ongoing struggle and ultimate triumph of good over evil.
Contemporary Hindu eschatology is linked in the Vaishnavite tradition to the figure of Kalki, the tenth and last avatar of Vishnu before the age draws to a close who will reincarnate as Shiva and simultaneously dissolve and regenerate the universe.
Most Hindus believe that the current period is the Kali Yuga, the last of four Yuga that make up the current age. Each period has seen successive degeneration in the moral order, to the point that in the Kali Yuga quarrel and hypocrisy are the norm. In Hinduism, time is cyclic, consisting of cycles or "kalpas". Each kalpa lasts 4.1 - 8.2 billion years, which is one full day and night for Brahma, who in turn will live for 311 trillion, 40 billion years. The cycle of birth, growth, decay, and renewal at the individual level finds its echo in the cosmic order, yet is affected by vagaries of divine intervention in Vaishnavite belief. Some Shaivites hold the view that Shiva is incessantly destroying and creating the world.
Islamic eschatology is documented in the sayings of the Prophet Muhammad, regarding the Signs of the Day of Judgement. The Prophet's sayings on the subject have been traditionally divided into Major and Minor Signs. He spoke about several Minor Signs of the approach of the Day of Judgment, including:
Regarding the Major Signs, a Companion of the Prophet narrated: "Once we were sitting together and talking amongst ourselves when the Prophet appeared. He asked us what it was we were discussing. We said it was the Day of Judgment. He said: 'It will not be called until ten signs have appeared: Smoke, Dajjal (the Antichrist), the creature (that will wound the people), the rising of the sun in the West, the Second Coming of Jesus, the emergence of Gog and Magog, and three sinkings (or cavings in of the earth): one in the East, another in the West and a third in the Arabian Peninsula.'" (note: the previous events were not listed in the chronological order of appearance)
Jewish eschatology is concerned with events that will happen in the end of days, according to the Hebrew Bible and Jewish thought. This includes the ingathering of the exiled diaspora, the coming of the Jewish Messiah, afterlife, and the revival of the dead Tzadikim.
In Judaism, the end times are usually called the "end of days" (a?arit ha-yamim, ), a phrase that appears several times in the Tanakh. The idea of a messianic age has a prominent place in Jewish thought and is incorporated as part of the end of days.
Frashokereti is the Zoroastrian doctrine of a final renovation of the universe when evil will be destroyed, and everything else will then be in perfect unity with God (Ahura Mazda). The doctrinal premises are (1) good will eventually prevail over evil; (2) creation was initially perfectly good, but was subsequently corrupted by evil; (3) the world will ultimately be restored to the perfection it had at the time of creation; (4) the "salvation for the individual depended on the sum of [that person's] thoughts, words and deeds, and there could be no intervention, whether compassionate or capricious, by any divine being to alter this." Thus, each human bears the responsibility for the fate of his own soul, and simultaneously shares in the responsibility for the fate of the world.
Researchers in futures studies and transhumanists investigate how the accelerating rate of scientific progress may lead to a "technological singularity" in the future that would profoundly and unpredictably change the course of human history, and result in Homo sapiens no longer being the dominant life form on Earth.[improper synthesis?]
Occasionally the term "physical eschatology" is applied to the long-term predictions of astrophysics. The Sun will turn into a red giant in approximately 6 billion years. Life on Earth will become impossible due to a rise in temperature long before the planet is actually swallowed up by the Sun. Even later, the Sun will become a white dwarf.