Niyala

Niyala as a planet is slightly smaller and less dense than Earth, though otherwise comparable in its overall geology and makeup. This results in a slightly lower gravity than Earth, and while this does not factor into game mechanics, it does influence some sciences that are available.

Additionally, air is substantially more dense — as such, fires burn hotter, flight is easier, and far larger creatures can exist as they can more readily fulfil their oxygen needs.

It is covered by only 65% water (compared to Earth's 71%), and has an axial tilt of roughly 27 degrees (compared to Earth's current 23). These two features combine to create a planet that has far stronger seasonal variation, with both summers and winters being intense.

Niyala is orbited by two moons, Plion and Noraz. This leads to more variable tidal interactions — often, the moons will cancel each other out or provide competing forces, but when in phase, this can cause intense tides. As such, few cities form on shallow coastlines and either remain some distance away from the shore, or build on higher bodies of terrain such as coastal cliffs or embankments.

Niyala's orbit is slightly slower than Earth's, taking 412 Earth Days. Fortunately (by sheer happenstance, of course), the more immediate time measures are consistent — hours, days, and weeks are identical. Months are close enough. You don't need to learn a new calendar.