Special relativity gives every mass in the universe its own clock. I have one, you have one, and every planet has one, but they only keep the same time if they have the same speed. General relativity adds that gravity alters time as well, as it slows down near a large mass like the earth. It then takes a lot of computing to make GPS navigation work, because the clocks of satellites tick at a different rates depending on their altitude and speed.
Why then does gravity dilate time? If time ticks by as network cycles complete, slower cycles slow down time, and more processing does that. Gravity as a processing gradient then slows time by increasing the network load. The matter of earth superposes its existence on the network around it to alter time, so a clock on top of the Empire State Building runs faster than one at the bottom. Gravity slows time as Einstein says, but by slowing down the quantum network, not time itself.
Would we live longer on a planet with more gravity? Others might think so, but we would experience the same number of time cycles. A larger planet dilates time relative to earth but the life events of our lifetime wouldn’t change.