According to our current understanding of physics, time dilation is a real phenomenon that can occur under certain conditions. Time dilation refers to the difference in the passage of time between two observers in different gravitational fields or moving at different velocities.
In the context of planets, time dilation can occur in extreme cases such as near a black hole or when approaching the speed of light. For example, near a black hole, the gravitational field is incredibly strong, and time would appear to slow down for an observer close to it compared to an observer in a weaker gravitational field further away.
However, in terms of an entire planet experiencing time at a significantly different rate compared to Earth on a regular basis, it would require highly unusual circumstances. It is not currently known if such a planet exists in the universe.
It's worth noting that there is no "universal clock" against which all other clocks can be measured, so the perception of time is always relative to a particular observer. Time dilation is a consequence of the theory of relativity and has been experimentally confirmed in various scenarios, including with atomic clocks on satellites and through particle accelerators.
In summary, while time dilation is a real phenomenon, it is typically observed in extreme environments rather than on entire planets. The idea of a planet where time consistently goes slower or faster compared to Earth under normal circumstances is speculative and currently unsupported by scientific evidence.