What do the white and black moons in Buddhist scriptures mean?

Bai Yue and Black Moon are concepts in the ancient Indian calendar. Bai Yue refers to the fifteen days from the new moon to the full moon, also known as day shift, white powder and white moon powder; Relatively speaking, the black moon refers to the day after the month to the first fifteen days of the new moon. In ancient India, the way to track the moon was to divide January into black month and fifteen white months. Bai Yue refers to the period from the new moon to the full moon, which was called "one day in Bai Yue to the 15th day in Bai Yue" by ancient Indians, while the first day to the 15th day of the black month refers to the period from the full moon to the front of the new moon, which is called "the first day to the 15th day of the black month". However, it should be noted that the habit of Indians is "black before white" for a whole month, so it is half a month different from the China lunar calendar. The following figure shows:

China lunar calendar Indian lunar calendar

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The sixteenth day of the twelfth lunar month, the first day of the black month (New Year).

1February 30th (root year) Black Month15th.

The first day of the first month (New Year) is the first day of Baiyue.

The fifteenth day of the first month in Bai Yue (this is written in black and white for a whole month).

The 16th day of the first month, the first day of the black month.

The thirtieth day of the first month, the fifteenth day of the black month.

The first day of February, the first day of Bai Yue.

…… ……

Baiyue 12th Five-Year Plan (Year Root)

On the other hand, when ancient Buddhism was introduced to China, the China monk Dade made a detailed comparison between the calendars of the two countries, thus determining what dates some ancient Buddhist festivals and fasting days should be in the lunar calendar in China calendar. For example, the date of Buddha's birth is equivalent to the eighth day of the fourth lunar month in China, and the Buddha's Happy Day (Arahara Festival) is equivalent to the fifteenth day of the seventh lunar month in China, and so on.

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