Here we will concentrate on the 13 moon calendar, based upon a cycle of 4 weeks, forming a 28 day cycle, (it takes 28 days for the moon to orbit the earth) over 13 moon phases to equal 364- the 365th being called 'the day out of time,' and serves as a public holiday in some countries. But what has this got to do with the Zodiac killer.
It is believed the Zodiac committed his crimes on a full or new moon, but this was not the case, for example, the July 4th 1969 or for that matter, the following day of the Blue Rock Springs attack, as it occurred close to midnight, were neither a full or new moon, only a waning gibbous moon.
But something does correlate with all four confirmed Zodiac attacks, that is, they all occurred on DALI days ie: the 1st, 8th, 15th and 22nd of each moon cycle, therefore the first day in each week of the 28 day cycle, represented by the crosshairs Dali symbol. Visit here for calendar and explanation. Leave this new window open on the calendar to enter the relevant dates.
There are 7 symbols of Dali, Seli, Gamma, Kali, Alpha, Limi and Silio for each day of one week.
So now we place the Zodiac crimes into place, starting with the Lake Herman Road murders on December 20th 1968, which is 12/20.
This falls on the first day of the week on the Dali line in position 8 of the Rythmic Moon. The Blue Rock Springs attack on July 4th 1969, which is 7/4, falls on the first day of the week again, on the Dali line once more in position 8 of the Cosmic Moon. The Lake Berryessa attack on September 27th 1969, which is 9/27, falls yet again on the first day of the week, on the Dali line in position 8 of the Electric Moon (remember the three circled 8's of the 'My name is' letter). Finally, a deviation to the normal Zodiac crimes and the murder of taxi driver Paul Stine on October 11th 1969, which is 10/11, and falls for the fourth time on the start of a week, on the Dali line in the 22nd position of the Electric Moon.
Therefore, all the four confirmed Zodiac attacks occur at the beginning of the week on the 13 moon calendar, which if the mathematics are correct, produces odds of 2401 to 1- which is pretty slim. Incidentally, it has been widely observed that the 'Halloween' card was depicting 13 moons in a subtle way, and not 13 eyes as commonly believed.
Continuing this observation to rule in or out any of the other Zodiac crimes, indicates the Modesto abduction of Kathleen Johns, the Cheri Jo Bates murder, the Betsy Aardsma murder and the Domingos/Edwards murders would all be ruled out, however, the Donna Ann Lass disappearance on September 6th 1970 and the Hood/Garcia murders would still remain a possibility.
Also, the disappearance and eventual murder of Judith Hakari on March 7th 1970 and Nancy Bennallack on October 25th 1970 in Sacramento, both fall on the first day of the week, as well as the Sleeping Bag Murders sometime on the night of July 4th 1970.
The 'Dripping Pen' card and 340 cipher, which contained numerous symbols of circles, partially or fully eclipsed, was mailed to the San Francisco Chronicle on the first day of the week on the 13 moon calendar, and along with nine attacks noted so far, would make this a highly credible argument or one hell of a statistical coincidence.
As a footnote, the Halloween Card mailed on October 27th 1970, depicted the moon and the earth on the envelope in the form of an Apollo 8 stamp.