"Willow on the Moon" refers to the time when the moon rises, and "after dusk" refers to the time when the sun sets. When the setting time of the sun coincides with the rising time of the moon, Ouyang Xiu's famous sentence "A bright future brings flowers to another village, and people will meet after dusk" will come true.

The setting time of the sun is related to latitude and longitude and solar calendar. The time when the moon rises is related to the latitude and longitude and the calendar.