Particle physicist Professor Brian Cox asks, 'What time is it?' It's a simple question which sounds like it has a simple answer, but do we really know what it is that we're asking?

In this intriguing documentary from the BBC's 'Horizon', Prof Cox visits the ancient Mayan pyramids in Mexico, where the Maya built temples to time. He discovers that a day is never 24 hours, and meets Earth's very own Director of Time. He journeys to the beginning of time, goes beyond it within the realms of string theory, and explores the very limit of time. He learns that we not only travel through time at the speed of light, but the experience we feel as the passing of time could be an illusion.

You will never see time in the same light again!