Yin QiMen (陰盤奇門) is different from the usual Yang QiMen (陽盤奇門) which make use of Upper, Middle, Lower Yuan (上，中，下 元) and JieQi (節氣). The limitation of Yang QiMen (陽盤奇門) is that it takes approx 5 days for a change in chart and is seen as a limitation in this modern fast pace environment when it comes to divination and tactics application.
In Yin QiMen (陰盤奇門) it makes use of lunar calendar as a primary cue for charts.
For example: 2019 Aug 13, 4pm is converted to Lunar dates as 己亥年，七月， 十三日，申時. This is then converted to 12 + 7 + 13 + 9 = 41. Using 41 divided by 9 and adopt the residue figure which is 5 as the choice of chart. With that, the Yin QiMen (陰盤奇門) for this hour is chart 5, thus using palace 5 to start the QMDJ chart.
Hence, every 2 hours there would be a change of chart. Making it efficient and align for divination and tactics application.