After dusk, which festival is the willow tip on the moon?

Yuan Xi, written by Ouyang Xiu, a writer in the Northern Song Dynasty. It depicts a touching picture: the moon rises at the tip of a willow, and a pair of lovers meet after dusk to spend a good time together.

The full text of Life Inspector Yuan is: Last year, the flower market was full of lights. The moon rose to the willow tree, and he met me at dusk. On the Lantern Festival on the fifteenth day of the first month of this year, the moonlight and lights are still the same as last year. I will never see my old friend last year again, and my tears are soaked through my clothes. This poem implicitly expresses a pair of lovers who love each other. They met at dusk, and in this year's Lantern Festival, they revisited the old place but did not see the Iraqi figure. Moonlight lanterns are still in full bloom, but I can't see last year's Iraqis, so I can't help crying my clothes.