which tracked the Synodic period of Venus.
This also corresponds to a saros, a period of approximately 223 Synodic months(approximately 6585.3211
The average time between the successive oppositions of Mars, its Synodic period, is 780 days;
As the Synodic lunar month is approximately 29.5 days,
the calendar uses alternating months of 29 and 30 days.
So first of all what is a Synodic Cycle and what is the significance of thirteen of them?
You also mentioned a Synodic Cycle and you said there would be thirteen of them starting in 2020.
COBRA: A Synodic Cycle is a cycle where two planets actually meet if you
look from the center of the Sun.
Because there are about twelve lunations(Synodic months) in a solar year,
this period(354.37 days) is sometimes referred to as a lunar year.
Because 223 Synodic months is not identical to 239 anomalistic months
or 242 draconic months, The 18-year saros periods do not endlessly repeat.
And when planets move in their orbits around the solar system, there is a certain period between the
first and second meeting of the same planet and this is called a Synodic Cycle.
This also corresponds to a saros, a period of approximately 223 Synodic months(approximately 6585.3211
days, or 18 years, 11 days, 8 hours), that can be used to predict eclipses of the Sun and Moon.