On Karwa Chauth day, the women keep fast and at moon rise time go to the roof to worship the moon for the long life of their husbands.
Karwa Chauth : Sunday, 8 October 2017
The same day is celebrated as Lord Shiva Family worship. Shiva's wife goddess Parvati is considered to be the symbol of eternal marital bliss. In every incarnation She gets married to Shiva. Through moon, the wives invoke Parvati to bless them also the same marital bliss She Herself enjoys.
Moon is symbolically pictured as the adornment of Lord Shiva's hair.
The moon also the god of medicines which indirectly means the blesser of the health and consequently the long life.