First off, it must be noted that, for convenience, their solar system is like ours; I don't have the astronomical or mathematical knowledge to make a different one. Mythical period: during this era, the calendar was lunisolar, and people used to understand the time of the day simply watching the sun in the sky. Predinastic period: the calendar turned from lunisolar to simply solar; the day was divided into 24 hours, 12 for the day, 12 for the night (though this number changed with the seasons, having more hours per day during summer, and more hours for the night during winter), and the day began at the sunrise. They used sundial to measure the time of the day, and merkhets for the night. The year was divided into 4 seasons (Spring, Summer, Fall and Winter), and every season was divided into 3 months of 30 days; at the end of the year, they added 5 days to fix the astronomical calculation. Revolutionary period: the calendar was changed, and even though it remained a solar one, more astronomical observations leaded to more precises calculations, and so they developed a calendar like ours. More precise instruments to measure the time lead to the creation of the concepts of minutes and seconds.
The Calendar and the seasons
The year starts with the first day of Spring, which is, for Eriu inhabitants, the first day of our March.
Spring: from 1st of March to 29th of May Summer: from 30th of May to 27th of August Fall: from 28th of August to 25th of November Winter: from 26th of November to 23rd of February.
Since every month in the Eriu calendar has only 30 days, there are, between February and March, 5 days before the end of the year (From the 24th to the 28th of February).
Holidays and Festivals
Festival of the end of the year (5 last days of the Eriu Calendar/24-28th day of February) This festivals is hold in honor of the Demiurge Cosmos, who created Eriu and defends it from Chaos. According to the Eriu tradition, these last 5 days are considered inauspicious, because it is when The god of the Sea assassinated Cheartas and ruled over Eriu until he was banished and chained to the bottom of the sea. This is also when Cosmos confined Chaos in the Tir n'Aill, the other world, and he took her with him. The festival last for 5 days long, and each day has specific celebrations, but there's one that occurs every day: the fight between Cosmos and Chaos. People dance around the streets in two snakes-like costumes: one white with rainbow feathers, representing Cosmos, and the other black, with red eyes all over the body(while Cosmos true form is know to Eriu inhabitants, Chaos has always been described as an "everwatching darkness", so people decided to represent him this way). This dance is a symbol of the continue batlle between good and evil, and if Chaos should prevail, Eriu would come to an end. Finally, in the last day, Cosmos defeats Chaos, and so the new year can begin. -The first day is a mornful one, in which people remember the death of Cheartas, god of Justice and first ruler of Eriu. They fast from sunrise to sunset, and at night, people light lanterns and candles and place them facing ovest, where are the gates to the Tir n'Aill, the other world. -The second day is dedicated to the searching for Cheartas body by Grian and Gealach. A common celebration for kids is searching for small eggs painted like beetles, to resemble Cheartas body parts. -The third day is dedicated to Nadur, goddess of life, nature and fertility. Before Cheartas' death, the earth was extremely fertile, it was a sort of never ending spring; but when the god was brutally slaughtered, and his pieces were brought together, the goddess gave away part of her power to bring him back to life! But one piece was missing: the heart, and so the god could walk among mortals only for a short period of time. After this, Nadur's power were not as strong as before, and this is how seasons were born. It is also a day to celebrate love: people can't celebrate weddings during this day, but they can "tighten the knot": during weddings, in fact, the lovers get their hands wrapped up in a ribbon, to recall the act of Nadur stitching up Cheartas, showing true love and devotion to him. In this day, people might wrap symbolically their hands again, to strenghten their bonds. -The fourth day is dedicated to the conquest of the Tir n'Aill, which used to be under the influence of The God of the Sea. -The fifth day is dedicated to the defeat of The God of the Sea, and to the beginning of the new year. This is the happiest day of the year, and yet the one that causes more apprehension: people celebrate all day long to invite the new year to come, and to remember the day they were set free from the domain of The God of The Sea, but they also wait for the next day, fearing that it might never come. As a final offer, they exibit marvelous fireworks all over Eriu, and finally go to bed. Rumours has it staying awake 'till dawn brings bad luck, because it's considered a lack of faith.
The day of the dead (10th of August) This day is celebrated in honor of Réalta (and later in honor of Anam too), to remember those who passed away. To understand this holiday, it is essential to underline how much the name is important in Eriu culture. Since the Eriu language is considered holy, people believe that speaking the name of a thing or a person gives life to it, even to the dead ones; so if your name is still spoken, you are not really dead, according to Eriu inhabitants. It is also believed that during this holiday the spirits of the deads can come back from the Tir n'Aill, the underworld, to visit their loved ones. It is during this holiday that the goddess Réalta was conceived, and since there is an annual meteor shower happening during the night, and since she is also the goddess of the stars, it is pretty obvious why this holiday is celebrated in her honor. We should expect people to mourn in this day, but instead Eriu inhabitants celebrate with joy. The first activity of the day is exposing tablets with the names of the deceased loved ones (those who can't write can usually afford to pay someone to write for them) in local altars. Relatives and friends join together to celebrate life and to spend time with the people they love, because life is short and unpredictable, so it must be enjoyed 'till the end. There's food, dancing and music everywhere, and people wear skeletal decorations for apotropaic reasons, that is to say to drive away evil influences, and to make the deads "feel at home". During the night, people gather together at the open air and light candles, so that their loved ones can find the way back to the Tir n'Aill, and they will turn them off only once the meteor shower is over. The day after, the altars are removed and the tablets with the name taken away, so they can be used the next years.