Spring
Every year when Persephone returns from the Underworld her mother Demeter allows Spring to return to the earth.
When Persephone emerges from the underworld, it marks the arrival of spring and the return of life to the world. This event symbolizes rebirth, growth, and the cycle of the seasons in Greek mythology.
Every year when persephone comes back to the underworld for six months after she leaves for six months
Persephone ate of the pomegranate in the Underworld and so had to return to the Underworld every year.
The Underworld.
Persephone rules the Underworld with Hades; she ate of the pomegranate so can not leave the Underworld entirely every year.
Persephone ate of the pomegranate in the Underworld, and thus every year must go to the Underworld - then return to Earth.
Demeter mourns her daughters lose every year, and winter comes to the earth. Persephone must go between the realm of Hades and the earth every year. Hades either must await Persephone or is with her.
Persephone lived in the Underworld six months of every year (winter) and aboveground with her mother Demeter during the other six (summer).
In Greek myth, it is because of the abduction of Persephone that the Earth/we know the seasons: for Persephone also ate of the pomegranate in the Underworld and every year must return between Earth/Olympus and Underworld.
Hades was joined by her every half year in the Underworld.
Persephone had ate the pomegranate in the Underworld; so had to return to the Underworld a part of every year.