秋分

秋分，是二十四节气中的第十六个节气，时间一般为每年的公历9月22~24日。秋分这天太阳到达黄经180°（秋分点），几乎直射地球赤道，全球各地昼夜等长（不考虑大气对太阳光的折射与晨昏蒙影）。古时有“春祭日，秋祭月”的民俗活动，秋分曾是传统的“祭月节”（中秋节），中秋节由秋夕祭月演变而来。

秋分的三候是：“一候雷始收声，二候蛰虫坯户，三候水始涸”。秋分作为“二分”之一，自古便受到从官方到民间的重视，也形成了丰富的节气民俗，包括祭祀、饮食、出行娱乐等方面。

In the Northern Hemisphere, the moment in time when the Sun stands directly above the equator while crossing from the north to the south is called autumnal equinox (also known as fall equinox, September equinox or southward equinox). It is the moment summer ends and autumn (fall) begins in the Northern Hemisphere (where nearly 90% of the world's population live). For the Southern Hemisphere, it is the vernal equinox (also called spring equinox) as it is the moment winter ends and spring begins.

在北半球，当太阳从北向南穿过时，太阳直接站在赤道上方的时刻被称为秋分（又称秋分、九月春分或南分）。这是北半球夏季结束、秋季（秋季）开始的时刻（世界上近90%的人口生活在那里）。对于南半球来说，这是春分（也叫春分），因为它是冬天结束和春天开始的时刻。

In the Northern Hemisphere the autumnal equinox occurs every year between September 21 and 24. The dates given on this page are based on Coordinated Universal Time (UTC), which for practical purposes is equivalent to Greenwich Mean Time (GMT - the time zone of the United Kingdom). While the autumnal equinox occurs at the same moment in time all over the world, the date and local time differ from place to place depending on the year and a location's time zone. For locations that are ahead of UTC (further east) it may fall on the day after, and for locations that are behind UTC (further west) it may fall on the day before. To find out the exact date and time of the autumnal equinox 2020 in your area use this seasons calculator.

在北半球，秋分发生在每年的9月21日至24日之间。本页给出的日期是以协调世界时（UTC）为基础的，实际上它相当于格林威治标准时间（GMT——英国的时区）。虽然秋分在世界各地都是在同一时间点发生的，但根据年份和地点的时区，各地的日期和当地时间有所不同。对于在UTC（更远的东部）之前的位置，可能会在第二天下降；对于落后于UTC（更远的西部）的位置，可能会在前一天下降。要找出您所在地区2020年秋分的确切日期和时间，请使用这个季节计算器。

The autumnal equinox is one of four days (two equinoxes and two solstices) throughout the year that mark the beginning of a new season. The other days are the vernal equinox (beginning of spring), the summer solstice (beginning of summer) and the winter solstice (beginning of winter).

秋分是一年中标志着新季节开始的四天之一（两个分点和两个至点）。其他的日子是春分（春夏）、夏至（初夏）和冬至（初冬）。

The word "equinox" is derived from Latin and means "equal night". On the day of an equinox, day and night are of approximately equal length all over the world, as the Earth's rotational axis is neither tilted away from nor towards the Sun. At all other times the length of day and night will be different.

“春分”一词来源于拉丁语，意思是“平等的夜晚”。在春分日这天，由于地球自转轴既不偏离太阳，也不朝向太阳倾斜，因此全世界的白天和黑夜的长度大致相等。在其他时间，白天和黑夜的长度是不同的。

Graph demonstrating the movement (caused by leap shifting) of the exact moment of the autumnal equinox between 1900 and 2520. X axis (bottom, horizontal): Calendar years, Y axis (left, vertical): day in September (21 to 23).

In a non-leap year, the moment of the autumnal equinox is about 5 hours 49 minutes after that moment in the previous year (in UTC), and in a leap year it is about 18 hours 11 minutes before that moment in the previous year, as can be seen in this graph. In this way the time of the autumnal equinox constantly shifts back and forth so it always stays between September 21 and 24. This four year cycle is clearly visible in the graph.

在非闰年，秋分点的时刻是在前一年的秋分后5小时49分钟（UTC），而在闰年，秋分点比上一年的秋分提前18小时11分钟，如图所示。这样，秋分的时间会不断地来回变化，所以它总是在9月21日到24日之间。这四年周期在图表中清晰可见。

To adjust for the gradual movement backwards on the calendar (as visible for the period 1900 to 2099), in years divisible by 100 (1900, 2100, 2200, 2300 and 2500 on the graph), which should be leap years as they are divisible by 4, the leap day is omitted (except when they are divisible by 400, eg. 2000 and 2400) and the moment of the autumnal equinox moves forward in time compared to the same moment in the year before.

为了调整日历上的逐渐向后移动（从1900年到2099年期间可见），在可被100整除的年份（图中1900年、2100年、2200年、2300年和2500年）中，闰日被4整除，因此省略了闰日（除非它们被400整除，秋分点的时刻比前一年的同一时刻提前。

FROM: Calendarpedia

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