Treatise on Armament Technology

Establish Day: Great good fortune.
Remove Day: Destroy the enemy.
Full Day: Military strength flourishes.
Balance and Settlement Day: Ill-omened.
In the traditional Twelve Divine Officers cycle, "Balance" (Ping) and "Settlement" (Ding) are usually two separate days, but are grouped here as a single unfavorable period.
Maintain Day: The army captures the enemy.
Destruction Day: Joy at first, followed by distress.
Danger Day: Not suitable for use.
Success Day: Great good fortune.
Receive Day: Joy at first, followed by misfortune.
Open Day and Close Day: Ill-omened.

The Verse Says:

The quarter moon meets the Emptiness mansion; the dark moon encounters the Bond.
original: "弦日逢虛晦遇婁" (Xian ri feng Xu, hui yu Lou). "Quarter moon" (Xian) refers to the 7th or 8th and 22nd or 23rd of the lunar month. Emptiness and Bond are two of the twenty-eight lunar mansions (constellations).
The New Moon God meets the Horn; the Full Moon seeks the Neck.
original: "朔神遇角望亢求" (Shuo shen yu Jiao, wang Kang qiu). Horn (Jiao) and Neck (Kang) are the first two lunar mansions of the Azure Dragon.
Emptiness and the Dipper, or a full moon with the Ox, lead to annihilation.
original: "虛斗盈牛為滅沒" (Xu Dou ying Niu wei mie mei). Dipper and Ox are mansions in the northern sky.
When nature dispatches the army on such days, all matters end in failure.

The "Days of Desolation between Heaven and Earth," the Five Voids, the Eight Exhaustions, and the Nine Bitternesses are most feared in local folk customs.
These are technical terms for specific clusters of unlucky days in the Chinese calendar. The "Five Voids" (Wuxu) usually refer to days where the elemental energy is depleted according to the season.