After the 30th day of the Lunar New Year in the year of the Rabbit (February 9, 2024), we will not have the 30th day of the Lunar New Year for the next few years, from 2025 to 2032.

Why are we missing the 30th day of the Lunar New Year?

The Lunar Calendar follows the moon’s phases and varies depending on the actual moon’s orbit around the Earth, rather than a predetermined repetitive pattern like the Solar Calendar. Therefore, the Lunar Calendar does not follow a set of rules like the Solar Calendar, and its variability is an important factor in ensuring the accuracy of the lunar months.

Lunar months closely follow the changing phases of the moon, from the new moon to the crescent, quarter, gibbous, and full moon, and back again. A lunar month begins on the day of the new moon, when the moon is on the same side as the sun. This moment is called the “dark moon” or “conjunction” and marks the first day of the lunar month. The length of time between two consecutive dark moons varies, resulting in lunar months of varying lengths.

We Won’t Have the 30th Day of the Lunar New Year for Several Years

On average, a lunar month is about 29 days, 12 hours, and 44 minutes long, with a variability of up to 7 hours. This variability leads to the phenomenon where the period from one dark moon (the first day) to the next can fall on the 30th or 31st day, resulting in months with either 29 or 30 days.

According to these calculations, the Lunar New Year’s 30th day will not occur again until January 31, 2033.

Why can’t we calculate the lunar months as precisely and predictably as the solar months?

Lunar months are calculated based on the length of a synodic month and the dark moon. These factors depend on variables that are not constant or predictable. As a result, the Lunar Calendar lacks a clear pattern and must be calculated precisely each month based on actual observations.

The upcoming eight consecutive years without the 30th day of the Lunar New Year is merely a coincidence and does not indicate a pattern in the calendar. Moreover, the Lunar Calendar has been in use for a long time in our country, and such occurrences are not unusual. For example, from the year of the Monkey (2016) to the year of the Rat (2020), there were consecutive years with a 30-day 12th lunar month.

Therefore, the absence of the 30th day of the Lunar New Year for several consecutive years is simply a consequence of following the Lunar Calendar and is not a cause for concern or something out of the ordinary.

Frequently asked questions

The Tet festival, or Lunar New Year, is a significant holiday in many Asian countries, including Vietnam. The festival is celebrated over the course of several days, usually starting from the first day of the first month of the lunar calendar and ending on the first full moon, which is typically around the 15th day. However, there is a mystery surrounding the absence of a 30th day during the Tet festival, which will not occur again until the year 2033. This anomaly is believed to be due to a combination of the lunar and solar calendars, where the lunar month is shorter than the solar month, resulting in a discrepancy that requires occasional adjustment.

The lunar calendar is based on the monthly cycles of the moon’s phases, with each month beginning on the new moon and ending on the day before the next new moon. A lunar month is approximately 29.5 days long, which is shorter than the 30 or 31 days of a solar month. To keep the lunar calendar in alignment with the solar year, an extra month is added every few years, known as an intercalary month. This intercalary month falls after the 12th month in a leap year, which occurs every two to three years. As a result, the length of the Tet festival can vary, sometimes lasting only 15 days and sometimes extending beyond, depending on the alignment of the lunar and solar calendars.

The 30th day of the Tet festival will occur again in the year 2033. This is due to the gradual shift of the lunar calendar in relation to the solar calendar, which will eventually bring them back into alignment. The occurrence of a 30th day during the Tet festival is a rare event, and the long interval between these occurrences adds to the mystery and intrigue surrounding this cultural tradition.
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