http://interfaithfast.org/
From that site:
"This fall, in an unusual convergence, many of our faith traditions share a season of sacred self-assessment and self-transformation. This holy season includes the month of Ramadan and the Night of Power (Islam); the High Holy Days and Sukkot (Judaism); the Feast Day of Francis of Assisi and Worldwide Communion Sunday (Christianity), Pavarana / Sangha Day (Buddhism) and Mahatma Gandhi's birthday. Some communities of the First Nations have already begun to observe Columbus Day as Indigenous Nations Day, with practices that transform its meaning.
Since each of our traditions recognizes the power of fasting as a spiritual discipline, we call on all people of faith to join in a fast from dawn to dusk on Monday, October 8."
On that site, it sounds like an American-only thing, but I don't see why it couldn't be international.