Why Would I Have Two Periods in One Month?

A year is a calendar unit. There are four solar terms in spring, summer, autumn, and winter. Spring is the beginning and end of the year. A year is about 12 months, excluding leap years, solar calendar 365 or 366, and lunar calendar 354 or 355 days.

One year

(Calendar unit)

1. The calculation of all crescent moons and the time when the solar terms appear is based on 120 degrees east longitude, which is the standard time of the East Eight District. However, the calculation of the lunar calendar before 1929 should be based on Beijing's local time at 116 degrees 25 minutes east longitude.

2. The day when the new moon appears is the first day of the month. If the time of appearance of a solar term is also on this day, regardless of whether the time of appearance of the solar term is later than the new moon, it will be counted as falling into the new month.

3 Every winter solstice always falls in November of that year. The period from the second day of the winter solstice of a year to the day of the next winter solstice is called one year old. If there are thirteen new moons in one year old, this year is a leap year and a leap month is added.

4 The first month without leap in leap years is Lei Yue. Because there are only twelve strokes in one year of age, at least one month in the next year without strokes, and there may be two months without strokes. But in this case, only the first month without gas is the leap month. The month before the leap month is several months, and the leap month is called the leap month.

The calculation rules for the lunar calendar listed above were adopted during the Shunzhi years of the Qing Dynasty, that is, in 1645 AD. An important feature of the above rules is that they are based entirely on astronomical observations in theory, without any mathematical relationship. This is in stark contrast to the solar calendar, which is determined entirely by mathematical relationships. Of course, for the calculation of the lunar calendar in the future, a mathematical model of the moon and the Earth's motion will still be needed, and this mathematical model with high accuracy is quite complicated. Without a computer, it is impossible for ordinary people to calculate an accurate lunar calendar. The mathematical relationship of the solar calendar is very simple. This forms another stark contrast.

However, if the lunar calendar of the current year is known, there is a very simple method to estimate the date of the Spring Festival next year. This method works for most years. Find the solar date corresponding to the first day of the lunar calendar on November 1st of that year. Decrease the number of months by ten and add nine to the number of months. If the date is in the following year, the solar calendar is January 22nd to February 19th. Between days, the Spring Festival is the day, and the error does not exceed one day before and after. For example, the November 1st of the lunar calendar in 2002 corresponds to the December 4th of the solar calendar, and the date of the 2003 Spring Festival predicted by this method is February 1st, which is the same as the actual date.

366 days a year

365 days a week