Although the Vietnamese and Chinese calendars are calculated based on the same principles, the differences in time zones have led to various discrepancies between the two countries’ calendars. The direct translation of data from Chinese sources by some publishers has resulted in unfortunate errors.
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| The Eternal Calendar book series. (Image: songhuong.com) |
Recently, there have been reports of discrepancies in calendar data. What is the actual cause? According to Mr. Tran Tien Binh from the National Calendar Department, the inaccurate data originates directly or indirectly from the many Eternal Calendar books available in the market, such as the Practical Eternal Calendar, General Study Eternal Calendar, and others. These Eternal Calendar books are printed with data translated from the Chinese calendar, and while promoting these books, authorities did not provide sufficient information for readers to understand that the Vietnamese calendar differs from the Chinese calendar! The differences between the two calendars did not just appear in 2006; they have occurred almost every year. Thus, there is nothing unusual about this year, just as there was nothing unusual in previous or future years as long as consumers continue to use the Eternal Calendar books.
The Vietnamese Calendar Differs from the Chinese Calendar
The Vietnamese Lunar Calendar (commonly referred to as the Lunar Calendar) is established based on government decisions regarding the time zone and lunar calendar used in Vietnam. While both Vietnamese and Chinese calendars are calculated using the same rules, the time zone difference (China’s official time zone is GMT+8, which is one hour ahead of Vietnam) causes numerous differences in dates, solar terms, and the Lunar New Year.
For example, both countries consider the new moon (the first day of the month) as the start of the lunar month. Recently, the new moon occurred at 11:05 PM (Vietnam time) on June 25, 2006; therefore, in Vietnam, June 25, 2006, is the 1st day of the 6th month of the Year of the Dog. However, according to Beijing time, this moment was already 12:05 AM on June 26, 2006, and June 26, 2006, is the 1st day of the 6th month of the Year of the Dog in the Chinese calendar.
The difference in the first day of the month leads to a month discrepancy between the two calendars. Since leap months are calculated based on the comparison of the new moon and solar terms, variations in these timings can result in differing leap months between the two calendars. For instance, in 1984, the Vietnamese calendar had no leap month, while the Chinese calendar included a leap month in October.
Calculating the Lunar Calendar requires complex astronomical modeling, which is not as straightforward as calculating the Solar Calendar or some other types of calendars. Therefore, publishers have often opted for the simpler method of translating directly from the Chinese calendar, which contradicts government decisions and causes confusion for the public.
Is Eastern Antiquity Affected?
Fields of study based on time, day, and month in the Lunar Calendar will naturally yield different results when using different Lunar Calendars. For example, horoscopes are entirely based on the birth date and time in the Lunar Calendar. Even parameters that are calculated using data that coincide with the Solar Calendar (i.e., similar to the Chinese calendar) must consider accompanying Lunar Calendar components that may differ. For instance, the star Tian De may shine on the day of the Snake in the first month, or the auspicious hour may fall into the hour of the Dragon on the day of the Tiger… The days of the Snake and Tiger may coincide between the two calendars, but the first month and the hour of the Dragon may differ!
To avoid errors, it is best for Vietnamese people to use the Vietnamese calendar. Mr. Binh recommends the following printed Vietnamese calendar books:
The Vietnamese Calendar 1901-1910 by Nguyen Mau Tung:
The Calendar and Historical Chronology of Twenty Centuries 0001-2010 by Le Thanh Lan;
The Vietnamese Calendar of the 20th-21st Century (1901-2010) by Tran Tien Binh.
For readers who have already purchased the Eternal Calendar, the book “The Vietnamese Calendar of the 20th-21st Century (1901-2010)” provides detailed information on the solar term changes, leap months, the Lunar New Year, and the varying periods between the two calendars. For instance, this year, the two calendars differ from June 25 to July 24 in the Gregorian calendar; in 2007, the difference was from February 17 to March 18; and in 2008, from November 27 to December 26 in the Gregorian calendar.
The book also notes that in 2007, the first day of the Lunar New Year (Tết Đinh Hợi) in Vietnam fell on February 17, one day before the Chinese New Year.
