The measurement of the passage of events in terms of their duration within a known frame of reference. Time is measured by regular subdivisions of the movement of the Earth through space, as it revolves on its axis (day) and maintains its orbit around the Sun (year), along with the orbit of the Moon around the Earth (month). As everyone knows, psychological time is variable, according to one's age and interest, with time seeming to pass more quickly the older one gets, and travelling more slowly when engaged in waiting for a pot to boil, for example. In astrology, each hour, day and month, their groupings and subdivisions, are given significance and planetary rulers. Greater periods are measured by the aspects of the planetary Chronocrators. Today an hour is fixed as 60 minutes, based on the rate of decay of radioactive atoms in an atomic clock. However, in earlier times, the hour was more flexible, being defined as one twelfth of the daylight period (or night), so only being sixty minutes as we know them at the time of the Equinox (although they could and did measure exact times with such devices as the hourglass and water-clock). Modern relativistic physics counts the concept of time as a fourth dimension of space, thus positing a four-dimensional space-time continuum, in which time is flexible and, relative to an observer, varies according to the acceleration and mass of an object. Advanced mathematics operates within an even greater number of theoretical dimensions, with the most radical suggesting (a bit like Buddhist philosophy) that limitless numbers of universes split off constantly and continue to exist and develop in other temporal dimensions. Mystical belief often states that time is an illusion, being purely the movement of our consciousness along the continuum, a way of organising the interwoven tapestry of existence. Both of these ideas are supported somewhat by astrology, because if prediction is possible, then the predicted event must at least in some sense already exist; moreover if the potential for free-will exists, then alternate dimensions must also exist, so that a "choice" can be made and the progressions and transits apply at a different level of awareness. It's a tricky concept...