Einstein tells us that the time you experience between two events depends on the path you take through the universe. In particular, it can depend on the curvature of spacetime along your trajectory. At a quick-and-dirty level: clocks in a strong gravitational field tick more slowly than ones far away from any gravity. (At the event horizon of a black hole, they wouldn’t tick at all.)
Or not so far away: James Chin-Wen Chou and colleagues at NIST have measured the difference in clocks that are separated by 33 centimeters in elevation. That’s one foot for you Americans. (See NPR, Science News, press release. And because this is a blog rather than Old Media, I’ll even link to the research paper in Science.) As predicted, the elevated clock ticks faster by a factor of (1 + 4×10-17). If you stand on a chair, you’ll move into the future that much faster.
Not a surprise, of course; it’s a straightforward application of general relativity. Still, we need to look pretty hard to find GR showing up on human scales. These guys worked very hard!