Is It Necessary to Use the Lunar Calendar for Birthdays?

 

The use of the lunar calendar is gradually disappearing

Many older generations still celebrate their birthdays based on the lunar calendar. The lunar calendar is a system based on the time it takes for the moon to orbit the Earth. To use the lunar calendar, we must align it with the widely used solar calendar. Our country's official calendar, the solar calendar, is a type of solar calendar known as the Gregorian calendar. In a regular year, it has 365 days, and in a leap year, an extra day is added, making it 366 days. Thus, the lunar calendar, based on the moon's orbit, does not align with the solar calendar, which is based on the Earth's orbit around the sun. For instance, November 1, 2022, in the solar calendar corresponds to October 8, 2022, in the lunar calendar. Because of this, when we fix our birthdays to the lunar calendar, the corresponding date on the solar calendar changes every year. Older generations, when their birthdays approach, must take the trouble to check the lunar date on the calendar every year. To avoid this inconvenience, more parents are now choosing to align their children's birthdays with the solar calendar. This reflects a trend where the lunar calendar, once deeply rooted in our daily lives, is gradually being replaced by the solar calendar.

February 29, which only appears every four years

The solar calendar is based on the time it takes for the Earth to complete one orbit around the sun. It takes exactly 365.24 days for the Earth to complete its orbit. Since the year is not exactly 365 days, we need to adjust this discrepancy. The calculation method is as follows:

Annual discrepancy: 365.24 days - 365 days = 0.24 days
Discrepancy over four years: 0.24 days x 4 years = approximately 1 day
Thus, every four years, we have one extra day based on the 365-day year.

According to this calculation, one day is added every four years. Therefore, in the solar calendar, one day is added to February every four years, making it February 29, a leap day. On leap years, people born on February 28 would see their birthday celebrated one day later.

 

A precise lunar birthday every 19 years

The lunar calendar is based on the time it takes for the moon to orbit the Earth. One lunar cycle takes approximately 29.53 days. The lunar calendar also has discrepancies. The calculation method for the lunar calendar's discrepancy is as follows:

1 year: 12 months X 29.53 days = 354.37 days
Annual discrepancy: 354.37 days - 365 days = -10.63 days
Each year, approximately 11 days are missing compared to the 365-day solar year.

When compared to the solar calendar, the lunar calendar falls short by 11 days each year, so a leap month must be added every 2 to 3 years. The reason lunar birthdays change is due to this large discrepancy. To reduce this discrepancy, seven leap months are added over 19 years in the lunar calendar. Thus, for 18 years, lunar birthdays move around, but on the 19th year, the birthday aligns perfectly with the date of birth. In other words, someone celebrating their birthday on the lunar calendar will have their exact birthday only when they turn 19. It takes 19 years to celebrate a "true" birthday. Why do older generations insist on using the lunar calendar, despite this discrepancy? The reason is that our ancestors have long used the lunar calendar. In traditional customs, important household events like farming, ancestral rites, moving, and weddings were all based on the lunar calendar. This long-standing custom has become ingrained, so many older people still believe the lunar calendar is more important than the solar one. Understanding this helps explain why some older people continue to adhere to the lunar calendar for their birthdays.

 

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