What is "zurvanism"

Zurvanism is a now-extinct branch of Zoroastrianism in which the divinity Zurvan is a First Principle (primordial creator deity) who engendered equal-but-opposite twins, Ahura Mazda and Angra Mainyu. Zurvanism is also known as "Zurvanite Zoroastrianism", and may be contrasted with Mazdaism, which is the surviving form of Zoroastrianism and in which Ahura Mazda and Angra Mainyu are either themselves primordial (the traditional view), or the 19th/20th century developments in which Ahura Mazda is no longer the Creator of only the good, but also perceived as the origin of Angra Mainyu.

In Zurvanism, Zurvan was perceived as the god of infinite time and space and was aka ("one", "alone"). Zurvan was portrayed as a transcendental and neutral god, without passion, and one for whom there was no distinction between good or evil. The name 'Zurvan' is a normalized rendition of the word, which in Middle Persian appears as either Zurvān, Zruvān or Zarvān. The Middle Persian name derives from Avestan zruvan-, "time", and which is grammatically without gender.