historically, there have been many calendrical systems in the Sea of Flowers, with no single calendar being widely adopted beyond a small region. as development of the beamrail system increased and rail guilds ran into the desire to unify time observation across their service areas, a single common calendar eventually arose in CC 1949, and has been accepted broadly in many locations.
the first iteration of what would eventually be the common calendar was designed in CC 1818 by an unknown figure within the Movement for Standardization¹, thought it would be relegated to the niche of only being used as a working calendar by a handful of organizations for most of the century. its major breakthrough was its adoption by the newly-formed Congress of Enlightened Scientists² in CC 1891, largely due to the efforts of Lamhar of Myeunsddoḱ, who gave the calendar alternate month names to represent various values and figures of the Congress. for a time, the Congress had decent connections with the leadership of various polities and guilds, leading to the spread of their calendar within business circles and private assemblydudes' meetings, so when business leaders started floating the idea of making a common calendar it was a natural pick to base it off of. the modern calendar³ was first put into use by the Tengexw Rail Guild and Thelexset Rail Guild, and quickly percolated out after, being adopted as an official working calendar by the Confederal Assembly and the government of Loëz within a year. at present, it's at least a fixture in most locations in the Sea of Flowers, often alongside local calendars, but some regions still haven't adopted it.
the common calendar is a solar calendar with 13 months of either 32 or 24 days, plus an additional end-of-year day outside of any given month, to represent the 377 days of the lilin year. months are split into either 3 or 4 weeks of 8 days each⁴, with 47 weeks in a year⁵. the year starts on the first day of the Autumn season, with the year-end holiday happening at the end of the Rainy season.⁶ years are counted from the start of Autumn in what was assumed to be the year modern flower cultivation was developed, which is considered CC year 0.⁷ accordingly, the current year is CC 1996, and the year the Heavenly Schism ended was CC 1633.
the months of the year are as follows:
¹ - the Movement for Standardization was an organization seeking to make various unified measures and systems for most aspects of daily life, based on repeating numerical patterns and specific numbers they viewed as important. most of their proposals didn't take off, though their dream of unified measures is very slowly manifesting as time goes on.
² - the Congress of Enlightened Scientists is a religious-scientific organization that hit its peak of relevance from the CC 1890s to 1910s, during a period of of increased mysticism around scientific progress. for a time, many major figures in the Sea of Flowers became converts, but the movement never really stuck, only persisting as a small church organization with minimal prominence.
³ - the main difference with the CES's version of the calendar was replacing the more religiously-oriented names with ones tied to natural phenomenon. the months are usually given in Alta, which is what's listed in the table, but other, less-used translations exist.
⁴ - going by the number of weeks, these follow the pattern 4-3-4-3-4-4-3-4-4-3-4-3-4, forming a pallindrome over the course of the entire year and generally (but not consistently) alternating between 3 and 4 week months.
⁵ - it's not uncommon to see the date given as year-week-day rather than year-month-day sometimes. traditionally there were also names assigned to each of the 47 weeks of the year, but these aren't all that common anymore.
⁶ - there are six generally agreed upon seasons: Autumn, Harvest, Winter, Spring, Summer, and Rainy. each season lasts around 63 days.
⁷ - there's no real evidence to point at this being the year flower cultivation emerged, and the process likely wasn't a single breakthrough like assigning such a date would assume. it's unknown why specifically CC 0 came to be the date assigned to that, but it's speculated to have emerged from some precursor to the religious-scientific movement.