Intercalary July

Watch out! See where the rainbow end? That's a perfect shot! The off licence...

Today is the 1st of intercalary July. Normally, ppl offer sacrifices to ancestors or ghosts on 1st, 15th and 30th. Therefore, right after yesterday's ceremony, another ceremony is on for the 1st of intercalary July. So, we are still in July, better not to travel / move house and better to stay at home.

In a typical lunisolar calendar, most years are lunar years of 12 months, but some years have an extra month, known as an intercalary or embolismic month. There are 7 of these intercalary months in the 19 years of a Metonic cycle.

The Chinese (Lunisolar) calendar date indicates both the moon phase and the time of the solar year. If the solary year is defined as a tropical year then a lunar calendar will give an indication of the season; if it is taken as a sidereal year then the calendar will predict the constellation near which the full moon may occur. It is based on exact astronomical observations of the longitude of the sun and the phases of the moon. The average length of the synodic month is 29.530589 days.

The mean time between between two successive vernal equinoxes is called a tropical year and it's about 365.2422 days. This means that it takes 365.242 days from the earth to make one revolution around the sun (the time is takes to orbit the sun). There are 12 new moons in a year, but it's 29.530589*12=354.367068 days. It is desirable to aligh the calendar with the seasons, and make the difference as small as possible.