Completely missed this one! It was yesterday.
In my defense, I am not married, so it is not very meaningful to me.
This is the married women's fast. For the day the wife does not eat (and in some cases does not drink either) for the entire day. In the evening she gets dressed up in fine clothes, sometimes her wedding clothes, and waits to see the moon. Once she sees the moon, either reflected in a pool of water, through a sieve, or through her shawl, then she can eat.
This fast is for the well fare of her husband, although I could have done it as part of preparing for and asking the Gods for a husband.
The day is, I am told, somewhat like the North Indian Valentine's Day. You can see it taking place in some Bollywood movies, for example it happens in Hum Dil De Chuke Sanam.
More information here:
This is yet another opportunity for me to be frustrated by the distance between myself and others who practice my religion. Granted, I let it slip and didn't notice what day it was. I found out because my Hindi teacher told me. She said, "I'm tired because today is Karwa Chauth."
"Oh I see," I said, "You must be feeling weak."
She continued as though she had not heard me, "You see, Hindu women fast on this day..." And she continued on giving me a long explanation of something that I already know while I smiled and nodded politely.
I've told her before that I'm a Hindu. It frustrates me that even when I say that, it is assumed that I don't know anything about it. I am educated and given explanations for things I already know all the time. I don't want to be obnoxious, though, so I don't say, "Yes, I know. I'm a Hindu, I do that too."
Naturally, when the Indian girl arrived in class she was told what day it was and not given the explanation, even though she is Christian and her family has been Christian for many generations. (Not that she didn't know what it was, of course she did, but I do also!) Argh.