Feiocious

Time dilation is an observed difference of elapsed time between two observers which are moving relative to each other, or being differently situated from nearby gravitational masses. An observer will see the other observer’s clock ticking at slower rate than his/hers. This effect doesn’t arise from technical aspects of the clock or the fact that any signal needs time to propagate, but from the nature of space-time described by theory of relativity.

Note the peculiarities of the effect as both observers see the other observer’s clock as being slower, counter-intuitive with our classically-built-logic: “I see your clock ticking slower than mine. Therefore, you’ll see my clock ticking faster than yours”.