According to the Lunar Calendar, not only in 2025, but also in the next 8 years, the lunar month of December will only have 29 days. It will not be until 2033 that people will celebrate the Lunar New Year on the 30th day of the Lunar New Year.
Explaining this, researcher Dang Vu Tuan Son, Chairman of the Vietnam Astronomy and Cosmology Association (VACA), said that the Lunar calendar is calculated according to the cycle of the Moon.
Accordingly, the light we see from the Moon is a reflection of part of the light it receives from the Sun. The Moon moves around the Earth, so we cannot always see its entire illuminated side, so there are full and waning phases...
"Because the Moon's phase cycle is neither exactly 30 nor exactly 29 days, but approximately 29.53 days (from one full Moon to the next), the lunar months alternately have 29 or 30 days to compensate to match the cycle," the researcher explained.
As a benchmark, Eastern astronomers used to take the completely moonless moment of each month - often called the "new moon point" - as the first day of the lunar month. The "new moon point" is when the Moon is in a position where its entire illuminated part is not facing the Earth at all.
"Thus, if the 30th day of a month ends but there is no "new moon" and we have to wait until the next day, then that month is a full month (has 30 days), the next day is the 1st of the following month.
On the contrary, if the "new moon" falls right after the 29th, the day that should have been the 30th becomes the 1st of the next month, and the previous month only has 29 days and is called a short month," said Mr. Dang Vu Tuan Son.
According to experts, the December of the year of the Dragon 2024 has a "new moon" point, according to precise astronomical calculations, falling at 05:26 on December 31, 2024 (Hanoi time). If we add 29.53 days, the next "new moon" point will be around 18:00 on January 29, 2025 (actually 19:35, due to many other factors causing fluctuations in the length of the lunar cycle).
Thus, January 29, 2025 becomes the first day of the new month, also the first day of the new year At Ty 2025. December 29 becomes the last day of the year Giap Thin. With a similar calculation, we can get relatively accurate results for the first day of the following years.
According to calculations, until the end of the year of Tan Hoi (2032), December will always stop at the 29th.
The expert affirmed: "This is purely a coincidence due to human convention. This has no natural cause, nor is it related to or has any effect on the weather cycle, but is only related to living habits and preparations for Tet."
On the other hand, it is not uncommon for a certain month of the year to be always short or always full for several years in a row. It is just that most of us do not pay attention to them like the end of the year.
