Today is a beautiful holiday. If you are American, you may not find this special occasion indicated on your calendar, even if your calendar like mine notes high Jewish holidays and the beginning and end of Ramadan and the feast of Eid al Fitr observed by Muslims.

This holiday is observed by more than a billion people around the world – nearly as many in number as Muslims – and yet Americans are relatively unaware of Diwali, the festival of lights. Hindus and some Buddhists celebrate the return of the god Rama from a period of exile, with people of southern India referring to the holiday as Deepawali or Dipawali. It’s a big holiday in the Hindu calendar, on par with the Christian celebration of Christmas, predating the same as Hindusim is the oldest living religion.

Sikhs also observe the same holiday, but in celebration of the release of a 6th century guru after being imprisoned. Yet another faith observes this festival; Jainists mark Diwali as the achievement of Nirvana by their religion’s esteemed founder, Mahavir Tirthankar.

The day is marked with special foods, sweets in particular, and among Hindus, the purchase of gold. In the evening small earthen pots are lit, like little votives, mimicking the candles which lit Rama’s way home. More contemporary and secular observation has included electric lights like those we Americans use at Christmas, along with fireworks at night.

Diwali is resonant with many peoples because it is a celebration of light out of darkness, at a time of the year when light is fading. Christians and Jews have Christmas and Hanukah, which celebrate their religion’s respective miracles of light over darkness; Wiccans and pagans celebrate the solstice, when the sun begins its slow return out of the deep of winter. So too do our global neighbors of central Asia share an archetypal feast of light.

Because the festival is observed on a lunar calendar, the date of the holiday varies each year, but is always in sync with the darkest point of the autumnal moon. Tonight’s new moon will offer no competition against Diwali lights. It’s also the fourth day of a five-day festival; the three previous days are more preparatory in nature, and the fifth day is spent celebrating with family and friends, just as Rama must have done after arriving among his people.

As you can see from the pictures posted here, the holiday is celebrated from India to Great Britain. And if you look more closely, perhaps some of your neighbors are celebrating. At one time while working for a Fortune 100 company I counted among my co-workers a number of Indian team members; I always enjoyed the tasty snacks they would bring in after the big Diwali festivities they had within their close-knit community, along with their families’ stories about this very old holiday. If you have Indian friends and co-workers, be sure to wish them a happy Diwali today.