The Earth may be 4.5 billion years old (give or take a few million), but this month, its inhabitants celebrate 40 years of helping it to stay green.Legend has it that Earth Day — developed by a Wisconsin senator in the 1960s to raise environmental awareness — was so named because a member of the organizing committee was celebrating a birthday. (“Earth Day” rhymes with “birthday.” Get it?) However it originated, the event’s purpose struck a chord in the hearts of many who recognized the need to protect their planet. Hence the inaugural Earth Day celebration on April 22, 1970, which gained the support of 20 million grassroots demonstrators and educators across the United States — and heralded the dawn of a huge environmental trend.Today, the “green” movement as we know it has reached cultures all over the world. (For example, last year’s Earth Hour event — which urged people to turn off their lights for one hour to conserve energy — tallied over one billion supporters on seven continents.) Environmental awareness has helped spawn major legislative actions (like the Clean Air Act) and governmental organizations such as the Environmental Protection Agency.Find all of the Valley’s Earth Day happenings here!Our region’s family-friendly geo-gala, the Hudson Valley 40th Anniversary Earth Day Celebration, takes place this month at the Dutchess County Fairgrounds in Rhinebeck and features Musicians for Clean Air concerts; farmers’ markets and organic food tastings; e-waste collections; GPS and Earth Caching treasure hunts; Doc Swan’s recycling magic shows; and tree planting. “It’s great to be involved with an event that educates so many on the environment,” says Laurie Rich, the celebration’s coordinator. “One of the coolest parts by far is the Swappapalooza,” she says. “[Participants] collect textiles and turn them into whatever they want — old T-shirts into reusable shopping bags, dresses into hats, quilts into puppets — that they can take home or even enter into a competition.”The two-day commemoration also aligns with the goals of the fairgrounds’ Green Initiative, which aims to make the 168-acre property and its facilities environmentally sustainable. According to Rich, the celebration will be the site’s first zero-landfill event; all solid waste generated by visitors will be recycled, composted, or transformed into energy by the zero-emissions Dutchess County Burn Plant in Poughkeepsie. “It’s so exciting,” she says. “It’s the biggest event for Earth Day in the Valley.”Hudson Valley 40th Anniversary Earth Day Celebration. Apr. 24-25. 10 a.m.-5 p.m. each day. $5, free for seniors & children under 12. Dutchess County Fairgrounds. Rte. 9, Rhinebeck. 845-876-4000 or www.dutchessfair.comEarth TunesValley moms are getting in on the Earth Day action this year, too. Singer-songwriter (and Westchester mom-of-two) Jennifer Marks, with the help of the Nature Conservancy, is releasing a family-friendly CD called My Changing Planet. Produced with three other moms from all around the country, Marks’ 18-track album — which features guest singers and actors like Joan Osborne, Noah Emmerich, and The Wiyos — contains entertaining stories and fun tunes that chronicle the Earth’s changes, and what kids can do to help. And the best part? All profits benefit the Nature Conservancy, whose worldwide chapters are dedicated to protecting threatened lands and waterways.Like what you hear? Pick up your own copy of the CD at any Whole Foods store or by visiting www.mychangingplanet.com. Or stream a song for free here.