William Strauss and Neil Howe in their books Generations (ISBN 0688119123) and The Fourth Turning divide Anglo-American history into saecula, or seasonal cycles of history, and divide the saecula into generations by birth year, and classify generations and historical periods into four types each.

As history molds generations, so do generations mold history. Modern Anglo-American history runs on a two-stroke rhythm. The two strokes are an Awakening and a Crisis.

• During an Awakening, rising adults are driven by inner zeal to become philosophers, religious pundits, and hippies, alienating children (who see the adult world becoming more chaotic each day) and older generations alike. Civil order comes under attack from a new values regime. Examples of Awakening eras include the Protestant Reformation (1517-1542), the Puritan Awakening (1621-1649), the Great Awakening (1727-1746), the Second Great Awakening (1822-1844), the Third Great Awakening (1886-1908), and the Consciousness Revolution (1964-1984).

• A Crisis is a decisive era of saecular upheaval. The values regime propels the replacement of the old civic order with a new one. Wars are waged with apocalyptic finality. Examples of Crisis eras include the Wars of the Roses (1459-1487), the Spanish Armada Crisis (1569-1594), the colonial Glorious Revolution (1675-1704), the War for American Independence (1773-1794), the American Civil War (1860-1865), the twin emergencies of the Great Depression and World War II (1929-1945), and The Rise of Islamic Terrorism (2001-Present)

A High is an era between a Crisis and an Awakening, and an Unraveling is an era between an Awakening and a Crisis. The most recent High was seen between World War II and The Consciousness Revolution. The most recent Unraveling was seen between The Consciousness Revolution and The Rise of Islamic Terrorism, a time of paradigm shifting.

The four types of generations are as follows:

• A Prophet (or Idealist) generation is born during a High, spends its rising adult years during an Awakening, spends midlife during an Unraveling, and spends old age in a Crisis. Prophetic leaders have been cerebral and principled, summoners of human sacrifice, wagers of righteous wars. Early in life, few saw combat in uniform; late in life, most come to be revered as much for their words as for their deeds.

• A Nomad (or Reactive) generation is born during an Awakening, spends its rising adult years during an Unraveling, spends midlife during a Crisis, and spends old age in a new High. Nomadic leaders have been cunning, hard-to-fool realists, taciturn warriors who prefer to meet problems and adversaries one-on-one.

• A Hero (or Civic) generation is born during an Unraveling, spends its rising adult years during a Crisis, spends midlife during a High, and spends old age in an Awakening. Heroic leaders have been vigorous and rational institution-builders, busy and competent in old age. All of them entering midlife were aggressive advocates of technological progress, economic prosperity, social harmony, and public optimism.

• An Artist (or Adaptive) generation is born during a Crisis, spends its rising adult years in a new High, spends midlife in an Awakening, and spends old age in an Unraveling. Artistic leaders have been advocates of fairness and the politics of inclusion, irrepressible in the wake of failure.

The list of generations and their types is as follows:

Note (1): Strauss and Howe use the name "13th Generation" instead of the more widely accepted "Generation X" in their book. The generation is so numbered because it is the thirteenth generation alive since American Independence (counting back until Benjamin Franklin's).
Note (2): The name "Generation Y" is also used in reference to this generation, as it is the generation following Generation X. There is no universally accepted name for this generation.

According to the above chart, generational types have appeared in Anglo-American history in a fixed order for more than 500 years, with one hiccup in the Civil War Saeculum. (The reasons for this is because according to the chart, the Civil War came about ten years too early; the adult generations allowed the worst aspects of their generational personalities to come through; and the Progressives grew up scarred rather than ennobled.)