Northern Winter Time

The calendar system primarily used by the Northerners to track the relative passage of time. Also understood and used in other parts of the Known World, though not applicable everywhere.
Uses astronomical events to determine the "months" - solstices and equinoxes.
The year starts with Winter.
Winter starts at the Fallpoint (equinox), and is terminated by the Springpoint (equinox). It lasts 180 days.
Summer is not an entity of its own; although the term is known, it is divided into spring and fall:
Spring starts with the Springpoint and ends with Midsummer (solstice). It lasts 92 days.
Fall starts with Midsummer and ends with the Fallpoint. It lasts 93 days.
Midwinter (solstice) is acknowledged, but usually isn't assigned much importance. The Fallpoint on the other hand is of much greater importance. The vehicles celebrate having survived another year and wish each other good luck for the coming year. It can be considered a collective birthday party that replaces celebrating individual construction dates. A vehicle is considered one year older when it lives to see the beginning of another winter; thus, a Northerner's age is stated in "winters".

Determining the Time

A newly built vehicle has no idea about what time of the year it is or how to determine it - the Matchmakers take care of teaching them this knowledge.
Using simple math, the number of days since the last significant celestial event can be counted and used to calculate the approximate date of the next one. This way, pretty exact estimations can be made. To account for leapyears and the fact that a year is not exactly 365 days long, adjustments are made to these calculations every once in a while.
For that purpose, or when one loses track of how many days have passed, a common way of telling the time of the year is simply looking at the shadows of various suitable objects at a certain time of the day. Using the knowledge how long the shadow is supposed to be at different times of the year, the date can be determined. The celestial events themselves are observed with the help of a vehicle's compass: During Springpoint and Fallpoint, the sun rises in the East and sets in the West. At Midsummer, the sun rises in the Northeast, and sets in the Northwest.

The calendar is often visualized as a circle that shows the three months and the cardinal directions of the sun's course at the different points of the year.