The system of Rayu calendar is difficult a bit. You can find out the Highbahha time corresponding to the current Earth time using the above tool, so basically, you convert dates using the tool. The time displays of Highbahha are confusing, so it’s better that you see the “地球で例えたら(to compare it to Earth)” to figure out what timeframe it is.

The details of the system are below, so they are difficult a bit though, read it if you want.

Being similar to the Japanese lunar calendar, Rayu calendar’s rule is a lunisolar calendar. There is a satellite called Haktol orbiting Highbahha, which is considered the moon, and the calendar is decided based on Haktol’s movements.

Because you have to understand the properties of Highbahha as a planet to consider Rayu calendar, let’s also confirm them.

Haktol completes one revolution around Highbahha in one month. The orbital period of Highbahha is 372.384007 [days], and the lunar month is 42.332108 [Hyberkha days], so a Highbahha year is about 8.7967 months. According to the lunisolar calendar, it’s based on the waxing and waning of the satellites, so one year needs to be divided into 8 or 9 months. When the year has 8 months, it’s called a common year, and when it has 9 months, it’s called a leap year.

Highbahha is orbiting around the fixed star as if the Earth is doing around the Sun. The angle apparent solar longitude is the value to indicate its position, so the word is used here. If the apparent solar longitude progresses from 0° to 360°, Highbahha can be considered to complete one revolution around the fixed star.

The times that the apparent solar longitude is reached 0°,90°,180°,270° are called vernal equinox, summer solstice, autumnal equinox, and winter solstice, and then if the time that has a full moon during the term from the vernal equinox(0°) to the next vernal equinox(360°) is eight times, it’s decided to be a common year, and if it’s nine times, it’s decided to be a leap year. The number of a year is about 339 days when it’s a common year, and it’s about 381 days when it’s a leap year. By the way, because the length of a year on Highbahha is 29.088705[Earth hours] on the Earth, to convert the Earth time, the number of a year is about 410 days when it’s a common year, and it’s about 462 days when it’s a leap year.

The day that includes the moment of a new moon for the first time since the time of a full moon is the last day of the month. Because the lunar month is 42.332108 [Highbahha days], there are two types of month: 42 days per month and 43 days per month. 42 days per month is called a short month, and 43 days per month is called a long month.

A year is divided into eight parts based on an apparent solar longitude, and they are called terms. The term from 0° to 45 is the 1st term, from 45° to 90° is the 2nd term, …, and from 315° to 360° is the 8th term. The number of terms is exactly 8 whether a common year or a leap year.

If the 1st term has a full moon, the month including the full moon is determined as the 1st month. It’s 2nd month in the 2nd term, …, and it’s 8th month in the 8th term as well. Usually, each term has only one full moon, but when it’s a leap year, there is a term that has two full moons. At this time, the month corresponding to the 2nd full moon in the term is called a leap month. For example, the leap month included in the 3rd term is called a leap 3rd month.

The names of months are defined. The months from the 1st month to the 8th month, and from the leap 1st month to the leap 8th month have the below names.

Fundamentally, a week has 6 days. The first day of the month is the 1st day of the week, the second day is the 2nd day of the week, …, and the next day of the 6th day of the week is the 1st day of the next week. But when it’s 43 days per month (long month), the only final week has 7 days and the 7th day appears. So the only 43th day of the month is the 7th day of a week. The names of the days of the week are below.

You can express the date as numbers like “xxx month xxx day” like the usual calendar, but in Rayu calendar normally, they call the month its name, and they call the day the name of its day of the week adding the number of the week. For example, when it’s the 2nd month, it’s called “Early Summer,” and when it’s the 14th day, because it’s the 2nd day of the 3rd week, it’s called “ⅢB.” Only when it’s the 43th day, it’s called “F+” for special. When it’s called linked like “xxx month xxx day,” it’s called linked like “Early Summer ⅢB.”

For example, Baysuke’s birthday is “2nd month 5th day, 519 in Rayu calendar” as numbers, but normally, it’s called “Early Summer IE.”

Those rules are unique to Rayu. Especially apparently, Wolf uses numbers normally instead even though they use the same calendar.

Because Baysuke and his friends’ birthday is based on Rayu calendar, these days differ on the Earth every year converting Earth time. On Highbahha, because the length of the year is longer than the Earth, their birthday doesn’t exist on the Earth in some years.

Below are Baysuke and his friend’s birthday examples. You can confirm them using the above tool, so try it.