阴历：月亮的轨迹与时间计算
The lunar calendar, also known as the lunar or the Chinese calendar, is a timekeeping system based on the cycles of the moon. It is widely used in various Asian cultures, including China, Korea, Vietnam, and other East Asian countries. The calculation methods of the lunar calendar have a rich history and are deeply influenced by culture and religion, making it an important time reference system in these societies.
The lunar calendar is rooted in the moon’s orbit around the Earth. It is based on the lunar month, which is the time it takes for the moon to complete one orbit around the Earth. This period is known as a synodic month and lasts approximately 27 days, 7 hours, 43 minutes, and 11.5 seconds. However, due to the Earth’s own orbital movement, it shifts position by about 27 degrees during the moon’s cycle, while the moon itself moves about 13 degrees and 15 minutes each day. As a result, to return to the new moon phase, it takes the moon approximately 29 days, 12 hours, 44 minutes, and 2.8 seconds, known as the synodic month.
The lunar calendar is calculated based on this synodic month. Since the number of days in a month cannot be evenly divided into the length of a synodic month, the lunar calendar employs two types of months: “big” months with 30 days and “small” months with 29 days. The first day of each month is determined by the day of the new moon, while the fifteenth day of each month is approximately the time of the full moon.
The lunar calendar’s new year starts with the new moon closest to the solar term of “Lichun” or the beginning of spring. However, there is a discrepancy between the lunar calendar and the solar calendar (Gregorian calendar) due to Earth’s rotation around the sun. A lunar year typically consists of only 354 days, which is about 11 days shorter than a solar year. This difference accumulates to approximately 32 days over three years. To reconcile this gap, a leap month, known as a “leap month,” is inserted into the lunar calendar every three years.
The leap month is usually inserted into a month that falls between solar terms but does not correspond to a specific solar term. Months that align with solar terms are called “full” months, while those in between are “empty” months. The year with the leap month is called a leap year, making it a year with 13 months, whereas non-leap years have 12 months.
In summary, the lunar calendar is a timekeeping system based on the moon’s cycles, particularly the synodic month. It employs the concepts of “big” and “small” months and introduces leap months to stay synchronized with the solar calendar. This ancient method of time calculation is still widely used in East Asian regions, providing a significant time reference for cultural and religious events.
阴历：月亮的轨迹与时间计算
阴历，又被称为太阴历，是一种基于月球运行周期的时间计算系统。它以月球绕行地球的周期为基础，被广泛应用于许多亚洲文化中，特别是在中国、韩国、越南和其他一些东亚国家。阴历的计算方法源远流长，深受文化和宗教的影响，是这些社会中重要的时间参考系统之一。
月球运行的轨迹称为白道，它是月球在天球上的轨迹，与太阳运行的轨道，即黄道，是两个重要的圆轨迹。月球绕地球一周需要的时间约为27日7小时43分11秒半，这被称为恒星月，是月球公转一周所需的时间。然而，需要注意的是，随着地球自身的公转，地球也在不断变化位置，大致前进约27度多，而月球每日行进约13度15分。因此，为了回到合朔状态，月球实际上需要约29日12小时44分2.8秒，这被称为朔望月。
阴历的月历按照朔望月的周期来计算。由于月份的天数无法完全整除朔望月的周期，阴历采用了两种不同的月份长度，即大月和小月。大月通常有30天，而小月只有29天。每个月份的初一是由合朔的日子确定的，而每个月的十五日左右则是满月时刻。
阴历的一年以接近立春的朔日为岁首。由于地球绕太阳公转约为月球绕地球的12又1/3次，这会导致阴历与阳历之间存在差距。一个阴历年通常只有354天，相对于阳历来说短了约11天。这个差距会在连续三年内累积到32天左右，因此，为了保持与阳历的同步，阴历每三年就需要插入一个闰月。
阴历的闰月通常是在有节但无气的月份插入的。有气月份是指与节气（如立春、清明、夏至等）相对应的月份，而无气月份则是介于两个节气之间的月份。插入闰月的年份被称为闰年，这样一年就会有13个月，而普通年份只有12个月。
总结来说，阴历是一种基于月球运行周期的时间计算系统，以朔望月为基础，采用了大月和小月的月份长度，以及闰月的概念，以保持与阳历的同步。这一古老的时间计算方法在东亚地区仍然广泛使用，为许多重要的文化和宗教活动提供了时间参考。
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