二至点是指天球上黄道距天赤道最远的两点，即北至点和南至点。它们分别称为巨蟹宫第一点和摩羯宫第一点。按照北半球的传统，分别称为“夏至点”和“冬至点”，合称“二至点”。
日地系统的另一个特点是二分点和二至点沿轨道逐渐运动。
Another characteristic of the sun-earth system is the gradual procession of the equinoxes and solstices along the orbit.
每年的二至点和二分点总会发生一些变化因为地球正改变着相对于绕日轨道面的自转轴角度。
From year to year, there is always some variability in the equinoxes and solstices because of the way Earth's changing tilt matches up with its orbit around the sun.
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