What does double yellow day mean?

Great ecliptic day and little ecliptic day.

Double Yellow Day is Big Yellow Day and Little Yellow Day. There are six auspicious ecliptic days on the great eclipse day, and the small eclipse day is arranged with twelve stars headed by the moon. Because there is no cosmic ecliptic day, it is called a small eclipse day.

The auspicious day in the zodiac refers to six of the twelve evil gods, namely Qinglong, Tiande, Yutang, Siming, Tang Ming and Jingui. When they are on duty, everything goes well and they don't avoid evil spirits. The auspicious day in the yellow calendar refers to six of the twelve duty days: elimination, danger, determination, persistence, success and opening.