Gravitational time dilation was first described by Albert Einstein in 1907 as a consequence of special relativity in accelerated frames of reference. In general relativity, it is considered to be a difference in the passage of proper time at different positions as described by a metric tensor of space-time.

Has time dilation been proven?

Physicists have verified a key prediction of Albert Einstein's special theory of relativity with unprecedented accuracy. Experiments at a particle accelerator in Germany confirm that time moves slower for a moving clock than for a stationary one.

When was time dilation first proven?

Time dilation isn't just theoretical; global-positioning satellites have to take it into effect to provide accurate readings to users here on Earth. And scientists have measured the phenomenon precisely in the field, most famously in 1976 with the Gravity Probe-A experiment.