절월·일진 기준
Twelve day officers
Twelve customary day designations determined by comparing the solar-term month branch with the day branch.
How did it begin?
The sequence is 建 (establish), 除 (remove), 滿 (full), 平 (balance), 定 (settle), 執 (hold), 破 (break), 危 (danger), 成 (complete), 收 (receive), 開 (open), 閉 (close). These are customary names with distinct meanings, not a single universal ranking of fortune for every activity.
Calculation rules
A day with the same branch as the solar-term month is 建. Each following branch advances one place in the sequence. A new month changes the starting point, so the designations are not a fixed uninterrupted 12-day cycle. The month follows solar terms rather than lunar months. For 2020–2050, it changes on the Korean Standard Time calendar date of each jie boundary, applying to the whole date rather than the exact instant. Missing required solar-term data leaves the value unavailable. WhatDay365 uses the device’s local date, changing the day at midnight (00:00). Lunar and day-pillar conversion supports Gregorian dates 1000-02-13 through 2050-12-31; dates outside this range are not estimated.