Senjitsu (八專・十方暮・庚申) (選日)

選日 SENJITSU — the ganzhi-period days of the Japanese almanac the koyomi annotations don't carry: 八專 (the twelve days 壬子→癸亥 — eight same-element 専日 that intensify all things and four free 間日; the sailors' rain-run), 十方暮 (the ten days 甲申→癸巳, 'all ten directions dark', eight of them stem-branch mutual destruction), and the sixty-cycle's VIGIL DAYS — 庚申 Kōshin (the sleepless night against the three worms 三尸, whose kōshin-machi raised the stone markers still standing at Japanese crossroads), 甲子 (the Daikoku vigil) and 己巳 (Benzaiten's feast). THE STRUCTURES ARE THEOREMS, proven from the five elements at load: computing wuxing over the spans DERIVES exactly the published 8/4 hassen split (間日 precisely 癸丑・丙辰・戊午・壬戌) and exactly eight 相剋 days in 十方暮 with the tradition's two known exceptions (丙戌, 己丑) — the lists derived, not transcribed. Definitions two-witness (the NDL calendar-exhibition/ja.wikipedia lineage + the koyomi-annotation references); day pillar from the shared lunar oracle; countdowns to each period and vigil served. Japanese becomes 16. Pure compute, no LLM.

Cost: 1 TIAN Points per call. tRPC procedure senjitsu.check.