In honor of International Day of Happiness on March 20, the United Nations has commissioned a series of postal stamps meant to represent the global ideal of well-being. Of the half dozen stamps the UN Postal Administration included in their final selection, only one was chosen to grace the cover of the holiday's promotional brochure as well -- to be, in effect, one of the most visible faces of world happiness. This year, that face belongs to a pit bull named Macy.

According to photographer Jaymi Heimbuch, Macy's story is one for reflection this March 20th. After the shelter where Macy was living deemed her "not appropriate for adoption," Macy was rescued by Grateful Dogs Rescue, a non-profit organization in San Francisco that cares for dogs at risk of euthanasia. Most dogs are fostered by volunteers until Grateful Dogs can find them permanent loving homes, but in Macy's case the two were one and the same: Jackie Shen, the woman who fostered Macy, fell so in love with the pit bull she decided to adopt the dog herself.

Heimbuch photographed Macy as a volunteer for Hearts Speak, another organization that promotes adoptable dogs to help find homes for them faster. After Macy's photo shoot, Heimbuch sold the images to a stock photo agency and her pit bull model got comfortable in her new home. It was only after a stranger alerted Heimbuch to the Happiness Day brochure that she learned her photo of Macy was the happy image of the year. Heimbuch said everyone -- especially Shen -- is "crazy thrilled" that Macy has been chosen to represent happiness around the world.

You can see the rest of Heimbuch's photos of Macy here.