An hour was a unit of time, 24 of which typically composed one day on Earth. (TV: Last of the Time Lords)
The space hour was used by the Tyrryxians. (COMIC: Size Control)
The Fifth Doctor once retrieved the Key to Time in less than one galactic hour. (GAME: The First Adventure)
According to Ashildr, ten thousand hours was all it took to master any skill and, after over a hundred thousand hours, one became the best there had ever been. (TV: The Woman Who Lived)