Fuenodian calendar

The Fuenodian calendar is the main calendar used to mark dates that occur on Fuenod. Because Fuenod, like almost all other planets, has different day and year durations, a calendar designed for the planet is required for many purposes.

Calendar format
The Fuenodian tropical year lasts for approximately 429.3671 Fuenodian days. Like on Earth, any calendar that assumes a fixed number of days for every year will accumulate drift over time. Hence, the Fuenodian calendar incorporates leap years. The leap years occur based around two cycles of different lengths: a 25-year cycle, and a 1000-year cycle. Leap years are assigned as follows: The above cycles give 367 leap years for every 1000 years, and hence an average calendar year of 429.367 days.
 * In the 25-year cycle, years 1, 4, 7, 10, 13, 15, 18, 21 and 24 are leap years. Whether year 25 of the cycle is a leap year depends on the 1000-year cycle.
 * In the 1000-year cycle, years 100, 200, 400, 500, 700, 800 and 1000 are leap years. These years coincide exactly with year 25 of their corresponding 25-year periods.

Like the Gregorian calendar, the Fuenodian calendar splits the year into twelve months, based partially on the period of Fuenod's moon Molvur (approximately 34.38 Fuenodian days). The lengths of each month are listed below: While the above table lists the Gregorian names, these are typically only used outside of Fuenod. Each nation typically has their own names for the months. The month names for three different Likkran languages are given below:

Traditionally, the northern hemisphere vernal equinox coincides with the beginning of March. As such, March and April represent the northern hemisphere spring, June and July the northern hemisphere summer, September and October the northern hemisphere autumn, and December and January the northern hemisphere winter, and February, May, August and November are considered the "transitional" months.

Conversion between calendars
Converting dates between the Gregorian and Fuenodian calendars poses a challenge, as not only the year lengths are different, but also the day lengths as well. The solar day on Earth is 86,400.002 seconds, while on Fuenod it is 88,893.280 seconds. Any conversion between the two calendars must take into account these differences, as well as possible time zone issues.

So far, in Innocence Seekers: The Black Rose, three comparison points are defined, using the Fuenodian calendar and the proleptic Gregorian calendar: