I'm writing a story involving multiple sentient species, interstellar travel, and a long history of colonisation. My main character is a Human living on the planet "Tender", whose ancestors colonised it from the planet "Ardel" a few centuries ago. Is it possible to arbitrarily write up the calendar based info (length of day, length of year, etc.) and deduce from this such things as size of the planet, distance from its sun, etc? For that matter, if all we know is the timekeeping details of a fictitious world, is that enough to deduce any other factors? For reference, my tentative values are this: Planet Tender has a 20 hour day and a 300 day year. Planet Ardel has a 33 hour day and an 80 day year. Assume a 60 minute hour in both cases. If one can't deduce much from this, what extra information is needed? All the material I've found so far starts with the star's characteristics, and then working down to the details of its planets. I want to work in the opposite direction if possible so I can specify certain conditions (day length, gravity, etc.) and work out any matching info (star type, climate, planet size, etc.).