here's an overview on the development of the dalassan calendar, the main calendar used on notasami.
first we need to go back 3000 years. in the mountains south of xesfar were the namar people, who, in 250 years, after conquering the city of dalassa, will form one of the largest and most influential empires in the history of notasami. just to be clear, 'namar' refers to the ethnic group, 'namak' is their language, 'dalassa' would become their largest city, and 'dalassan' refers to the empire run from that city. think 'latin' vs 'roman' for simplicity's sake.
the traditional namar calendar was based solely on the moon. they recognised six phases of the moon; not considering quarters true phases but rather just a borderline between gibbous and crescent. the full moon was particularly revered and a minor celebration was held to coincide with it. this naturally lead to the development of months, starting on the full moon, lasting 27 or 28 days. the number of days per month and the pattern of lengths of months was never fixed, it was always directly determined from the moon. there were 14 months in a year.
months were in reality seen as countdowns until the next full moon; giving a 'date' in ancient namak had you say how far out from the next full moon you were, unless the full moon was indeed that day, where you would say which full moon in the year it was. so here we can see that days were numbered backwards; the 2nd day of the month was actually the 27th/26th, and the name of the first day of the month quickly became synonymous with the name of the month, though since days were counted backwards, the name actually applied backwards; meaning the first month of the year was called 'the second full moon'. its confusing if i try to explain it but trust me it makes perfect sense
so, after the namar founded the dalassan empire, this calendar soon proved to be inefficient, disliked, and downright annoying to work with. this was due to two main factors.
the namar were usually mostly pastoral, occasionally also raiding nearby groups, slowly transitioning to agriculture just before the formation of dalassa. a lunar calendar is not well suited to agriculture since it does not account for seasons. for a society just becoming agricultural this isn't much of a problem, but when they start a massive empire with a huge economy dependent on agriculture, it's not good.
the dalassan empire was huge. lots of different ethnic groups were subsumed under it, and the dalassans were notable for letting them continue their practices, culture, and speaking their own languages. however, lots of these cultures had festivals and rituals that depended on seasons and specific times of the year. this is problematic when administration uses a lunar calendar where your festival days have to be calculated to different times every single year, like easter.
this problem was solved by turning the lunar calendar into a lunisolar one by dropping the second-to-last month every 9 years. (because, remember, the last month is technically a countdown to the first full moon, so it's not possible to remove it). the calendar was additionally standardised such that every month was 28 or 27 days in an alternating pattern. this was a good enough fix for ancient times but it kept getting improved over the next 500 years for increased accuracy. further additions included the dropping of a day twice every 9 years, adding a day every 27 years, and not dropping the second-to-last month every 720 years.
the dalassan calendar was developed just before the advent of bunapunism; which started in dalassa and eventually spread globally, and with it came the calendar. since this calendar was more or less "fixed" rather early on, this meant that it was spread more or less "finished" from the get go. some places still kept some minor differences and developed tiny quirks of their own, but consensus was pretty uniform throughout history and any kinks like that were eventually ironed out by or during the modern period. while religion was the best indicator of the spread of this calendar, it also spread albeit at a more limited pace based on trade, such as in yafu, where in some places the dalassan calendar was adopted centuries before bunapunism became widely practised. of course, later on, the calendar was exported to and/or imposed on the rest of the world by colonialism or globalisation in general, though many indigenous calendrical systems still survive, often limited just to liturgical practice.
a full "formal" description of the calendar as it currently stands is on my website








