The title of this blog contains the words “500 Years” so we need to show why 500 years is an important period of time, what I call a basic cycle. It is long enough to be a period where many changes happen, and short enough that we have had several during recorded history.

First let’s consider the periods of revolution of the outer planets. This is similar to the Moon rotating about the earth, though in this case these planets are rotating about the Sun. The Moon takes about 27 1/3 days to go around the Earth, as measured from, say, 0 Aries to 0 Aries.

Planet	Period	Number of Periods	Total Years
Jupiter	11.86	42	498.12
Saturn	29.42	17	500.14
Uranus	83.75	6	502.50
Neptune	163.74	3	491.22
Pluto	245.33	2	490.66

The average of the five cycles is 496.53 years. This is not to say that all these planets return to the same position in about 500 years, but only that their relative positions return. Also note that the inner planets not mentions have such small cycles that they of course fit into this scheme. The longest cycle of those not mentioned is Mars, which is only two years.

Next let us consider the synodic period of two planets. This is the period between one conjunction of the two planets and the next conjunction. After the first conjunction the two planets move and so the next conjunction takes place after, and perhaps long after, the faster moving planet returns to the spot where the first conjunction took place. This is similar to the period from one New Moon to the next New Moon. As the Moon moves during 27 1/3 days the Sun moves almost one-twelfth of its total rotation (as seen from the Earth) and so the Moon needs to move a little more after it returns to the spot of the first conjunction – New Moon. That is why consecutive New Moons advance through the zodiac. The synodic period for the Moon-Sun is about 29 ½ days.

The average is 500.60 years. This is a relative return of all these cycles.

To sum up, there is a basic cycle of 500 years in which all the planets of the solar system return to their same relative position. This 500 year cycle is the basis of the title of this blog, The 500 Year Party. The next question of course is when does the 500 years start. This is similar to the question of when the 20 year Jupiter-Saturn cycle starts. The Jupiter-Saturn cycle has long been used in astrology; I have seen it in a book of ancient Persian astrology, where it was said to rule the rise and fall of kings. In present times, the cycle starts near the beginning of an even decade, so I call this period the bi-decade and it consists of an outgoing half – from conjunction to opposition – like the lunar cycle from New to Full Moon, the waxing cycle. Then the odd decade – from opposition to next conjunction – like the phase from Full to New Moon, is the waning period. So waxing decades are the Sixties, the Eighties, and the Oughts, whereas the waning decades are the Seventies, the Nineties, and this current decade. I’ll leave it to the reader to find the differences between the waxing and waning decades.

There is another large astrological cycle called the Great Year, based on the Precession of the Equinoxes whereas the first point of Aries – the Vernal Equinox – moves backward through the zodiac at a rate of approximately one degree every 72 years. This causes the Pole Star to change through the ages, and results in the charmingly named Age of Aquarius, which is due any time now. The Great Year is about 26, 000 years. The actual year consists of 12 months, but 52 weeks or 13 4-week periods. This difference between 12 and 13 is the result of attempting to merge the lunar – moon-based – and solar – sun-based calendars. But the ratio of a week to a year is about the same as the ratio of 500 years to the Great Year, so I call this 500 year cycle the Great Week.

From: Astrology: Worlds Visible and Invisible Everett Blackman AFA 1974