History of the Kasshi Calendar

The Kasshi calendar is traditionally said to have been created by chiNrasta in 2969 BOE, the same year as the Revelation. It has since been modified multiple times to produce both the modern solar calendar and the lunar calendar.

Pre-chiNrasta

Prior to chiNrasta's creation, the calendar was based purely on observations. A new month began with the first observation of the new moon. The naming of months was, as now, based on the seasons. The months were:

• Spring
  • Walītra (Early Spring)
  • Wakunrī (Mid-Spring)
  • Walenkalel (Late Spring)
  • Wevvalī (Additional Spring)
• Summer
  • Wamūtra (Early Summer)
  • Wakommū (Mid-Summer)
  • Wamūnalel (Late Summer)
  • Wevvamū (Additional Summer)
• Fall
  • Watreshtra (Early Fall)
  • Wakontresh (Mid-Fall)
  • Watreshnalel (Late Fall)
  • Wevvatresh (Additional Fall)
• Winter
  • Wadreftra (Early Winter)
  • Wakondref (Mid-Fall)
  • Wadrefnalel (Late Fall)
  • Wevvadref (Additional Winter)

The fourth month in each season was only used in some years. A month was considered to be Early Spring/Summer/Fall/Winter if it was the first month after the Sun had passed the starting points of those seasons, and then the following months, until the next season, were named accordingly. Thus, some years would require four months in a particular season and other years would only require three.

ChiNrasta's Calendar

ChiNrasta desired a calendar that would be predictable, rather than relying on observations, thereby allowing a single calendar to be used everywhere. The observation-based calendar could occasionally result in different cities being off by 1 day or even, in rare cases, a whole month. The basic principles were the same as the current calendar, but with far less precision.

Half-seasons

Segments were not yet measured out. At the time, reasonably accurate information was known only for eight points - the solstices, the equinoxes, and the midpoints of those. Measurement precision was only to the level of ¹/₂₀

day (3 daymins).  This established 8 half-seasons

Half-season	Days	Daymins
Spring I	27	30
Spring II	26	54
Summer I	28	15
Summer II	31	3
Fall I	33	51
Fall II	34	39
Winter I	32	51
Winter II	29	48

Note that these lengths are quite different from the length they would take today, due to almost 4 millennia of precession. ChiNrasta divided each of these half-seasons into 9 segments, for a total of 72 segments. It was assumed that each segment took the same length of time. The segments were then grouped into 12 solar periods of 6 segments each, which gave a rough approximation of their length, but with a margin of error of up to about 21 daymins.

The length of the sidereal month was known to somewhat greater precision, to the tenth of a daymin, as 18 days 10 daymins, 6 daysecs. It was established that the Moon traversed 3²⁶/₂₇

segments each day.  Thus, as today, the position of the Sun and Moon would be computed for each day.  If the Moon was 0-3 segments ahead of the Sun, it would be counted as New Moon, 4-7 segments as Upper Fasting, etc.  Skipped days were more frequent at this time due to the relative coarseness of the segments, and consequent greater "rounding errors".

Months were named according to the segment the Sun was in at the time of the New Moon. Consequently, it would be one month ahead of the modern calendar about half the time.

Early developments

ChiNrasta was aware that the information she based the calendar on was incomplete. As a result, she ordered the establishment of an observatory to collect data on solar and lunar movements to refine the calendar. Careful solar observations were made to determine the length of each segment, beginning in the year 5 YF. By the year 125 YF (2845 BOE) sufficient data had been gathered to produce half-daymin-precision estimates of the length of each segment. The lunar movement was also redefined as time per segment rather than segments per day, and was defined as 15 daymins, 8 daysecs, 25 daythirds per segment, refined to 27 daythirds by 125 YF. At this time, precession was not yet known. As a result, there was no accommodation for precession and, in fact, the values that were produced were rather the average of 120 years. The values produced by these observations were used for the calendar for several centuries. The following values were produced:

Solar period lengths
Month	Days	Daymins
Early Spring	18	32
Mid-Spring	17	56
Late Spring	17	57½
Early Summer	18	32½
Mid-Summer	19	38½
Late Summer	20	59½
Early Fall	22	18½
Mid-Fall	23	4½
Late Fall	23	3½
Early Winter	22	16½
Mid-Winter	20	57
Late Winter	19	35½

In the year 267 YF (2703 BOE), the definition of months were changed from the solar period New Moon is located in to the solar period the Full Moon is located in.

Precession gradually became more noticeable over the centuries, as the Ivets Observatory continued to keep careful records of the segments' starting times. By the time that the errors had accumulated to a noticeable size, however, the Empire had fallen, and there was no central authority to impose a new calendar. Several reforms were adopted in different areas, causing different states to have different calendars. The first solar variant was adopted by around 1500 BOE. By this time, the error had accumulated to almost 4 days in Fall and Winter.

In 836 BOE, with the establishment of the Rata Incarnation of the Empire, the various alternate calendars were replaced by a Reformed Calendar. The Reformed Calendar was the first to incorporate precession. The distinction between the sidereal and tropical years was recognized. Each segment was split into quarters, creating a total of 288 segments, ensuring that no segment would last longer than a day. The segments were established with an accuracy down to the tenth of a daymin, based on the sidereal year, and the first precession rule was established, namely, the year was shifted by 1 segment every 75 years. Further observation and the discovery of the Laws of Orbital Motion permitted calculation of greater precision. By the fourth century BOE, the solar calendar was becoming increasingly common, and the segments were doubled once more to 576 segments when it was noted that it would soon become possible that a future shift would cause a 243-day solar year with the size of the segments, as the longest segments were just slightly smaller than 1 day. A further halving created the modern calendar.