This is a straightforward request for the ability to play around with the length of days (in hours), the length of months (in number of days per month), and the length of years, in both days, and number of months to a year.).
So that we might decide that a particular world had days which lasted 27 hours, weeks that lasted 12 days, months that lasted 6 weeks, and years that lasted 5 months.
Additionally, that we be able to come up with (mod in?) names for days of the week, and months of the year, with the possibility for creating-and naming-a cycle of years (which would either randomly, or progressively, assign "year names" from a list).
Furthermore, to be able to assign names to those constellations, and moon/moons, in the night sky that surround (and influence?) the world. That we be able to assign each constellation a number of days (a period of days from one date to another) when they are "prominent", and to assign to the moon (or each moon) a number of days it takes that particular moon to go through the cycle of new-full-new.
Also, that we be able to assign certain dates as "holidays", once we've got the cultures in place to honor them.
Finally, that we be able to assign temperature and percipitation scales to various seasons, to be able to name those seasons, and to decide approximately how long each season lasts.
It would also be very nice, if we could fill in some descriptive text for certain of these entities (the months, the constellations, the moons, the holidays), that might then pop up occasionally-easter egg fashion-when those times happened, in-game.
I'm not sure how much of this has already been requested (I had no idea what to search for, frankly), and I know it'll likely be a long time until we see something like this going into the game, but I atleast wanted to mention it.