The Empress controls the seasons and the time of day across the entirety of the Sea of Stars, indeed the seasons and day length are universal across the all the lands, via her control of the Sun.
The year in the Sea of Stars is thirteen months long, each month consisting of twenty-eight days (divided up into four weeks, each of seven days); Fall, Winter and Spring are each three months long while Summer lasts for four. The Empress’ Birthday an extra-calendary day is placed in the middle of Summer making a total of three hundred and sixty-five days a year.
While some cultures maintain their own calendars, most use the Imperial calendar for taxes and official business, it is easier (and safer) to coordinate with the Imperial officials after all.
While many cultures and traditions look back on the time before the Sundering as a Golden Era before the dragons ruined everything, the dragons themselves rarely look backwards in time, nostalgia has no place in their make up. The majority of dragons live looking forward, making plans for decades or ever centuries in the future, though a small few are pure sensualists that live only in the present and near future. People are advised to avoid the sensualists among the dragons as they are mercurial in mood and very dangerous to more fragile creatures.
While one can use magic to travel forward in time is the Sea of Stars, traveling to the past is impossible.
Notes: Y is a another tricky one, so just some cultural bits for the day.
Image Clocks: a watch-maker seated at his workbench with a long-case and a bracket clock behind him, diagrams of movements above his head. Engraving. From the Wellcome Collection. License Attribution 4.0 International (CC BY 4.0).
Sea of Stars RPG Design Journal 