《晋书·志·第一章》
太阳走黄道围绕着极点运行，而极点北面距离黄道一百一十五度，南面距离黄道六十七度，冬至、夏至时的止息处就有了时间上的长短之分。 
日行黄道绕极，极北去黄道百一十五度，南去黄道六十七度，二至之所舍以为长短也。 
The sun travels the ecliptic around the extreme point, and the extreme point is 115 degrees north of the ecliptic and 67 degrees south of the ecliptic. The point where the sun stops during the winter solstice and the summer solstice determines the difference in the length of day and night.