In general relativity, the rate at which a clock runs depends on its position in a gravitational field. Observers at different gravitational potentials can compare elapsed time and find a difference. The video introduces this idea through the planet in Interstellar, where time differences help drive the story.
The physical effect and the film example
Relativistic effects must be calculated for specific conditions, including mass, distance and motion. The film’s ratio of “one hour to several years” should not be applied as a general value. NASA Goddard explains that relativistic differences in clock rates and frequency shifts matter for GPS systems; see the NASA Goddard reference.
This page focuses on the gravitational-field effect and links to a broader introduction to time dilation. It is not a time calculator or a numerical analysis of the film scene.
Original video: Watch the source video on YouTube.