Earth's 24-hour day is the baseline for all human timekeeping, but Einstein showed that time is not absolute. A clock at a higher altitude (weaker gravity) ticks slightly faster than one at sea level — a real effect corrected daily in GPS satellites, which would otherwise drift by 10km per day.
Special Relativity adds velocity-based dilation: a clock moving at high speed ticks slower than one at rest. At 10% of light speed, the difference is tiny (0.5%). At 90% of c, clocks tick at 43.6% of the normal rate. At 99.9% of c, just 4.5%.
The Earth level of the Cosmic Dashboard shows a live clock in your local timezone and includes two interactive relativity simulators: a black hole proximity slider (Schwarzschild radius multiples) and a light-speed slider (0–99.9% of c). Both show two clocks running at different rates — yours and Earth's — so you can feel the dilation in real time.