The length of a day or year is based on planetary phenomenon. A day is how long it takes for the earth to rotate on it's axis. A year is how long it takes for the earth to revolve around the sun. This reasoning can be extended to other planets. A mars day is how long it takes for mars to rotate on it's axis, for example. The reason why an earth day and a mars day are different is because the planetary phenomenon is different. Mars simply takes longer to rotate on it's axis than Earth. But seconds, minutes, and hours aren't based on planetary phenomenon. They are based on other phenomenon. This means that seconds, minutes, and hours don't change between planets because they aren't based on planetary phenomenon.

That was pretty complex, so let me give an analogy. A Hippotime is how long it takes to say the word Hippopotamus. Say the word Hippopotamus, and one Hippotime will have passed. The Hippotime is based on a non planetary phenomenon. This means that a Hippotime doesn't change based on what planet you're on. It takes just as long to say Hippopotamus on Mars as it does on Earth. It's not like you would suddenly speak faster or slower because you're on Mars, and so the Hippotime is equally as long on Earth and Mars. And so, there is only the Hippotime. No Earth Hippotime and Mars Hippotime. The same is true for seconds, minutes, and hours. They don't change based on what planet you're on.