ronomical constants appearing in the <i>T&#224;ich&#363;</i> almanac (太初曆) used at that time. He renamed the almanac the <i>S&#257;nt&#466;ng</i> (三統曆) and introduced the concept of <i>t&#224;ij&#237; sh&#224;ngyu&#225;n</i> (太極上元) or simply <i>sh&#224;ngyu&#225;n</i>. It was an epoch at midnight on a ji&#462; z&#464; day in a year with a sexagenary cycle of ji&#462; z&#464;, and with the following unusual astronomical phenomena: lunar conjunction, winter solstice, the beginning of an ec