The winter solstice marks the shortest day of the year. On this day, the sun hangs below the horizon for the longest amount of time; at the Earth's pole, it does not rise at all. Compared with the rest of the year, Sol's radioactive energy is the weakest on this day. Immediately following the winter solstice, Sol's time in the sky begins to grow.

During the Late Roman Empire, those who worshipped Sol as a supernatural deity believed that the winter solstice, which takes place around December 21 in the Northern Hemisphere, represented the death of Sol. For three days, Sol would remain low: changes to the timing of the sunrise and sunset remain so small in the days following the solstice that people cannot tell the difference without clocks. In fact, solstitium literally means when the sun stops moving. However, after roughly three days, Sol's time in the sky begins to accelerate more quickly. Ergo, on December 25, the followers of Sol would celebrate Dies Natalis Invicti, the (re)birth of the unconquered sun.

The vernal equinox, or the beginning of spring, marks the transition from majority darkness to majority daylight. This Holy Day celebrates the growing strength of Sol, along with its effects on weather patterns, biological life, and human bodily function.

The Summer Solstice represents the peak of Sol's yearly power: it is the longest day of the year in terms of sunlight, and Sol's radiation is strongest on the Terran surface.

The autumnal equinox, or the beginning of fall, marks the transition from majority daylight to majority darkness, as Sol's time in the sky diminishes. This Holy Day emphasizes reflection on the past summer season and preparation for the meteorological and biological changes to come.