 on <a href="QinHanSolarTerms.html">this page</a>, we see that before <span class="nowrap">N<sub>-162</sub></span>, the dates of the winter solstice (Z11) were all in month 11 and all leap years coincided with the years in which the lunation fractions of Z11 (and Z12) were greater than <span class="nowrap">12/19</span>. After <span class="nowrap">N<sub>-162</sub></span>, the leap month pattern was interrupted and the dates of Z11 were no longer fixed to month 11. Instead, the dates of Z12 were all in month 