Understand planetary triggers and you will understand a great deal about the astrological timing of events. The principle is very simple. The outlying planets of the solar system, Uranus, Neptune, and Pluto can take months, even years to travel over a given point. When they create configurations or aspects with each other or with sensitive points on your birth chart, they generate a great deal of energy.
Then a rapidly moving inner planet acts as a trigger, setting off the energy like a detonator setting off an explosive and you experience an event or an epiphany. These are the types of planetary action that act as triggers.
Change in direction: The release in energy when a retrograde planet turns direct can be a trigger. When a planet is retrograde it appears to move backward in the sky as seen from Earth. During the time it is retrograde it cannot express its energy directly, one reason for the legendary computer glitches and scheduling snafus associated with Mercury when it is retrograde. When it slows and reverses direction, that energy releases.
Another trigger is a quickly moving planet that touches an outer planet or completes a planetary configuration by transit. The inner planets: Sun, Moon, Mercury, Venus and Mars, will not stay for more than a day or two unless they are preparing to turn direction, but that is long enough to trigger an event.
A third trigger is a new or full moon. It can be an ordinary new or full moon, or it can be an eclipse. While both new and full moons and eclipses can act as an energy release, an eclipse can precipitate change on its own if it is impacting your chart. In that case, the eclipse point will be right on the planet in question, in opposition (180 degrees), or square (90 degrees) from a planet or significant point.
A trigger does not operate in a vacuum. When there is no pertinent activity by outer planets or secondary progression, the fast moving aspects indicate a short-term set of conditions that quickly pass with little consequence.
The more loaded your chart, meaning the more outer planet activity touching your chart’s planets and other pressure points, the more likely a trigger will set off an event.
Astrology has the advantage of giving you the heads up so you know the nature of the energy that is building up and the areas likely to be affected by an event. By keeping your eye on planetary triggers, you also get a heads up on the likely periods an event will happen.