Every year, women in north India (mostly) keep a fast on Karva Chauth for the whole day in order to wish for a long life for their husbands. At the end of the day, when the full moon rises at night, they break their fast.
They worship the moon and then look at the moon through a sieve.
And then they look at their husbands through the same sieve. After some more rituals, the husbands feed the women thereby breaking the fast.
Nowadays, men keep a fast too and then they break it together.
There are many interesting stories and reasons behind this day but what does stand out is that this day strengthens the bond between two people.