. <i>L&#236;</i> contained a system of mathematical astronomy developed to perform these calculations. Calendar calculation was just one of the calculations in a <i>l&#236;</i>. Thus, a better translation of <i>l&#236;</i> is <i>astronomical system</i> or <i>almanac</i>. Hereafter I will use <i>astronomical system</i> and <i>almanac</i> interchangeably.</p><p>All Chinese astronomical systems specified a <i>l&#236;yu&#225;n</i> (曆元), which was a time origin from which time was measured for almanac calcul