The world is called Bardel, and the Twingate area lies in the country of Sanjun. Sanjun is a human kingdom. The current monarch has left Twingate more or less alone -- he is called Gorlen, as all Sanjuin kings in known history have been. His original name is lost.
The world has no moon. Instead, another heavenly body rests in the sky, brighter than a star. It is variously known as the Watcher, the Traveler, or the Heir. The watcher sits just to the side of the sun in the summer, and strays from the sun as the seasons change, until in deepest winter the Watcher is only visible at night.
Even years are warmer -- very much so, in fact. Twingate's weather in even years is more or less like a slightly-drier Seattle or Portland, or like a wetter Tahoe -- snow in the fall and winter, but sun in the summer. In odd years, it is colder. Farmers have a harder time getting crops to grow, it snows more, and the sun seems fitful and wan. The weather in Twingate in odd years is more along the lines of Canada or Alaska. The coldest month in any year is Tenmon, where the Watcher comes out only at night and the sun seems to shrink and fade. This is said to be the time when ghosts and evil spirits are at their strongest -- in the darkest days of this month, even undead who are normally dormant during the day walk freely, and good folk stay inside as much as possible and hang charms over their windows. The DayWithoutLight comes in the middle of Tenmon -- a day and a half (thirty-six hours) where the sun does not shine. When that dark day is over, the sun comes up, and clocks are reset, as the sun comes up at what would have been sunset before. With its new start, the new year can begin -- either with bright and sudden warmth in even years, or a slow, grudging return to spring in odd years.