Last Sunday marked the beginning of Ramadan, the holiest month of the Muslim year. If you're a non-Muslim and don't know anything about Ramadan, this brief article at Vox.com covers the essentials. Muslims believe Ramadan to be the month God revealed the first verses of the Quran to Mohammed. It's a time of contemplation and celebration. There are an estimated 3.3 million Muslims in the United States, so there's a possibility you know someone or will run into someone who's observing it. As a shorthand for those of a Christian background, think of it as a cross between Lent and Christmas. Like Lent, it's a time of reflection. Unlike Lent, Ramadan sounds extremely demanding. Instead of just giving up one thing for the season (I've known people who have given up chocolate, for example), Muslims fast all day every day. They eat and drink water before sunrise, and don't consume anything again until sunset. And like Christmas, at the end of Ramadan people come together for celebratory meals and exchange presents with loved ones. Ramadan ends July 5. Until then if you're not Muslim and you're in a seat on the bus or subway during your end-of-day commute and see someone standing who you think might be Muslim, it would be a nice gesture to offer them your seat. They haven't eaten anything all day.