Not every planet has a night: very small planets have not enough mass to block much sunlight. However, as they grow big in scale, the dusk zone also grows. This is truer in orbits closer to the sun, where desertic climates are common. At the temperate middle orbits it's easy to have bright nights due to the clouds acting as lush reflecting screens. But even if the confortable darkness of night is a luxury for some, it becomes the norm far from the sun: behind all the cloud layers piled up, the planets are gradually subsumed in penumbra.
The very concept of a day is certainly diffuse in the Disk as whole. Every planet has its own rotation cycles, and there is not an unified unit of time. A traveler in planet A can build a house from the foundations to the roof during a single night. Then go to planet B and have seven dusks and dawns pass over him during a nap. But most people don't travel too much, and adapt their lives to their local idiosincrasy as part of their planet culture; just as all civilizations adapt to summer and winter. But how much exactly does a winter last?
Translation cycles are equally diverse across the known world. And while using years as an unit can work when talking with a fellow planeteer or organizing local stuff, the proper way to deal with strangers or speaking of the past is in terms of generations: "In times of my father, my grandfather, or my grand-grandfather". However, seasons do exist, and every planet gets their summer, fall,
winter and spring. They just have a different impact and time on each. I cannot imagine how hard (an long) can winter be on one of the outernmost planets, and how does their people endure, if there is actually somebody there.
Sometimes, a sage tries with more effort than success to research notes, contrast planetary records and make sense of the world history, and eventually surrenders; cursing the disinterested nature of men; because it's very hard to find records of the past of any kind in the planets beyond personal or familiar diaries. "Maybe people would act different if we all lived in a planet with the same years and days for everyone" he says. "We could measure our ages in years; or know which planet holds the oldest city" But only sages care about that kind of impossible things: nobody else cares about when something happened or what is their exact age. A kid becomes a youth at some point, and then an adult, then an old man. Those ages are most times obvious to oneself and to others, and they don't need more. While for the sages the world is old and carries the weight of the past, for those with fire in their bellies the world is as fresh as the everchanging sand in a beach, waiting for them to build their castles on; and its easy to hear the breath of the gods behind you, just as if they had created the world not long ago, and are still taking a rest.
Weather, on the other hand, is much more important.
The Disk itself looks like a disk, because the known orbits all spin in the same plane. Just like planets, clouds and winds have their own cycles around the father sun. And just as birds migrate from planet to planet, alongside floating flower seeds, stray projectiles or the harmless paper hearts that young girls like to send into the sky so they find their future lovers, also winds and storms are put to dance by thermal and centrifugal forces and attracted eventually by a planet's pull. However, weather's dance is as vital to farmers and navigators as planet's dance is to the sages. A weather yearly almanac, be it copied from another guildsmen or inherited through many generations is an invaluable treasure to have for men and woman of many trades. When there is no other choice, settlers and pioneers write them by their own hand, many times in the improvised symbols and crude drawings proper of illiterate men.