This is mostly a scratchpad to post notes on Taura's concalendars and related stuff as I'm writing again the article about it, but feel free to put stuff about your conworld's calendars as well.
The Megadelanean Calendar (also known as the Euremegadelanean, Bredezhan and Midonid Calendar) is the time reckoning system used by most peoples in Bredezhanya, among them the Hellesans. The calendar is almost as old as the amount of years it reckons, and its last iteration was established in the Council of Midònia, in 1860 MR (Megadelanean Reckoning).
Since Taura is Earth in a parallel timeline, natural years are like ours, and reckoning years tend to have 365 days in hybrid calendars (360 in some lunar calendars). The Bredezhan Calendar consists of 12 months in a 365-day year. Summer solstice marks the end of spring and the beginning of summer, but also the new year. The last day of the year is bressaures 5th, followed by the first day of the year, brans 1st. A new day begins at sunset.
Each year is divided into four large times that correspond to seasons, each one having three months of the calendar, more or less. All months have 30 days, except bressaures which is a special division with only 5 days; it is known as gui(g) preninci "half week", because weeks are 10 days long. Each month has exactly three weeks, which means that all months start with the first day of the week, dimarn, and finish with dirols, week's last day. The days in bressaures are not named, only numbered, so dirols, 30 na cenller (the year's last big month) is followed by bressaures, which is followed by dimarn, 1 na brans.
A rough comparison with the Gregorian calendar gives the following:
1st. Brans / June 21 to July 20
2nd. Arges / July 21 to August 19
3rd. Feres / August 20 to September 18
4th. Berm / September 19 to October 18
5th. Bruine / October 19 to November 17
6th. Riçold / November 18 to December 17
7th. Mavendres / December 18 to January 16
8th. Rovanyes / January 17 to February 15
9th. Àster / February 16 to March 17
10th. Bers / March 18 to April 16
11th. Martighes / April 17 to May 16
12th. Cenller / May 17 to June 15
Half week. Bressaures / 16 to 20 June
In leap years an additional day is added at the end of bressaures, making it a half-week of 6 days. The additional day is added every four years, but every 33 years the last leap year takes place after 5 years; and so on.
To sum it up.
Megadelanean leap years in sky blue. Gregorian leap years in pink.
Megadelanean years don't exactly match with Gregorian years because those begin with the summer solstice, so the coincidence period is from June 21st to December 31st. Consider this when consulting tables like the one above.
The combination of seasons and months results in this typical pattern:
ISEU "summer"; from Peran isaura "hot flush". Brans apocope of Bramsard, the deity that assures the fertility of fields and animals, from Peran Baramasarata "reaper bull". Arges from Sarden Argymai Festia "Festa's tears", the name given to the Perseids. Feres from Peran Ferais, related to Common Megadelanean Faris "Sirius".
NAUSARD "autumn"; from Elnid nausarth "decay, fatigue, weariness". Berm from Peran nbermauas "pilgrimages to the woods". Bruine from Peran broduinar "herds of mist; flocks of fog". Riçold from Peran Ritiaudas "wind freezer", a nature deity that announces the arrival of winter.
ARBOÇ "winter"; from Elnid arabarth "stagnation, stoppage". Mavendres "weddings of cats". Rovanyes from Peran Rubanies "(feasts) of the wolves". Àster "disturbingly tumultuous, ravishing".
MADISSAIVE "spring"; from Sarden madisaeues "sweet fruits". Bers from Peran Baire, the deity of flowery plants. Martighes from Peran malestigazi "pilgrimages to the mountains". Cenller related to Hellesan cenard llir "kingly cereal, royal corn".
Bressaures from Peran brēnas saurus "five suns". Solstice day is named Armallard, from Elnian Armail Ardar "Sun on the top".
Ancient cultures like Sates and Perans had lunar calendars without the concept of week as we understand it. Months were divided into smaller periods of time accordingly to lunar phases. With the adoption of 30-day months these were divided into two equal halves, the fortnights, of 15 days each. Later, when Sardens made further adjustments to the calendar, Perans created 5-day weeks by dividing the fortnights into 3 parts. The last step in the creation of the current Megadelanean week was to unite two Peran weeks into 10-day weeks, and adjusting them so each month had three weeks.
The names of days vary from language to language, but they are usually the result of naming days after deities or weekly tasks. The Hellesan names begin with di, which is the short form of Peran dinaki "24h day". The first five days have names of Peran origin, the oldest of all, and the last five are the new additions after the creation of 10-day weeks.
The days of the week are:
Dimarn "day of the Great Ones", from Peran dinaki Maremnas. Devoted to the Great deities of the Megadelanean pantheon, the so called 'Twelve'. It was the only truly festive day in Ancient days, and people named it, jockingly, dinaki Marnu "(the) Great Day". Nowadays it's one of the three festive days of the week. Dinçolà "day of the Home-ones; Day of the domestic ones". Devoted to the home deities and the ancestors. Originally it was a half-festive, and people spent the day cleaning the house and doing the other domestic tasks, so people jockingly referred to that day as dinaki tedule (day of (doing) the house), irreverent form of dinaki Tedulani. Didac "Idachi's Day". Dedicated to Idachi, one of The Twelve. Dinfers "Ferseu's Day", the national hero of Perans. Dinare "Niare's Day". Dedicated to Niari or Niare, the moon goddess. Disturs "rusturs' Day". Dedicated to the natural genies of forests, mountains and wild lands. Dirines "irines' Day". Dedicated to the genies of calm waters. Dibardes "pardenyes' Day". Dedicated to the genies of the land and the countryside. Dintarmes "tambres' Day". Dedicated to the genies of the underground. Dirols "erols' Day". Dedicated to the genies of the atmospheric skies.
Days (dinci "24h day") have the same length as ours, but they are divided into 36 hours of 40 minutes each (onç "40 minute hour"). As we said a new day begins at sunset, unlike our days, which begin at midnight. In the table below you can see the Bredezhan day compared to ours. As you can deduce, davenalle stands for "midnight" and daussort means "midday"; therefore giane "sunset" and aurefoys "sunrise".
To each half of the 24h day correspond 18 oncis. Hours are numbered from 1 to 36, the first one being the one after sunset. The hours are reunited into groups of three, six of these corresponding to night (nalle) and named gisles "vigils", and the other six to day (sort "day(light)") and named jancis "day time".
Vigils and daytimes are named accordingly to characteristic traits or associated ideas:
• Tasyare "silent calm". Considered the most tranquil part of the day, when animals return to yards and, people, to home.
• Brossar "(to have) supper". The hours dedicated to the day's last important meal.
• Entressatze "abed one". The hours to go to bed.
• Brantallons "intempestive hours". Considered the most untimely and less productive hours in the whole day.
• Natjambre "terrible night". Considered the worst part of the night, for being dark and deep hours in which spirits and night beings roam ways and fields.
• Fesyellet "rooster's call". The hours previous to sunrise. when roosters crow the most. Considered the best hours to share secrets.
• Laude "golden one". The hours after sunrise, when light takes golden and pinkish shades.
• Tregolança "bustling", "feverish time". The hours when work is most intense.
• Sarçol "sun's crown". The three hours previous to midday.
• Daunir "(to have) dinner". The hours dedicated to that meal. And to after-dinner's nap.
• Ainocandh "evening's falling". The last hours in which there's still enough light to work outside.
• Morsandh "dark entering". The hours that open the path to night.