What time period does meridian mean?

According to the modern circular clock, the pointer points vertically downwards to 6 o'clock and vertically upwards to 12 o'clock.

In the ancient sense of China, the meridian time means that the sun and the moon appear in the sky at the same time on the day of vernal equinox and autumnal equinox (about 18 o'clock), with an offset of just five or five minutes (the sun and the moon are in the same diagonal on the celestial sphere), so as to achieve the average of the essence of the sun and the moon.

However, most divination data prove that the positive meridian represents 6 o'clock in the evening, when Yin and Yang are on average.