The Jewish calendar is lunisolar: the festivals, the days, the months and the years are based on the time taken by the moon for its revolution around the Earth, the seasons for the time taken by the Earth for its orbit around the sun. Solar and lunar years differ by about ten days. To recover them, some embolismic years were created, with 13 and not 12 months.
The calendar begins with the month of Tishrì (September and October). On 1st and 2nd of Tishrì falls Rosh ha-shanà, New Year's Day, the day of creation. At Rosh ha-shanà the food must be sweet, the bread is round shaped, and the seeds of wheat and corn are planted. The 10th of Tishrì falls Yom Kippùr. It is the day of total abstinence from food, dedicated to prayer and penance. Before Kippùr moral and material debts towards others must be settled and it’s necessary to ask forgiveness to those who have been offended. It ends after 25 hours with the sound of the shofàr. The 15th of Tishrì is Sukkòt, the "Feast of Tabernacles". It is a reminder of those in which the Jews lived for forty years in the desert after leaving Egypt. In agriculture it marks the last harvest before winter. They eat and spend part of the day in a wooden hut (sukkà). The last day of Sukkòt is Oshanà rabbà. Sheminì ‘Azzeret ("eighth day of gathering") is an extension of the festival of Sukkòt and is the last day that they go into a sukkà. The next day is Simchàt Torà: the reading of the Torah ends and begins again. It is one of the three festivals (with Pesach and Shavuòt) called "pilgrimage festivals" because in ancient times the Jews went to the Temple of Jerusalem. The 25th of Kislev (November-December) is Channukkà. It Commemorates the re-consecration of the Temple of Jerusalem (164 BC) after the victory of the Maccabees on Antiochus IV Epiphanes and the miracle of the oil lamp which lasted eight days instead of one. A light is lit for eight days every evening of Channukkìa. The celebration is close to the winter solstice, when the hours of darkness are greater than those of light. The 15th of Shevat (January-February) is Rosh ha-shanà la-ilanòt, or New Year of the Trees. It marks the end of winter and the awakening of nature. The 14th Adar (March) is Purim. The book (Meghillath) of Queen Esther is read; she saved the Jews of Persia from extermination 2.500 years ago. It's a Carnival in which children wear fancy dress. The 14th Nissan (March-April) is Pesach, Easter or "Feast of Unleavened Bread". It reminds us of the exodus of the Jews from Egypt and the end of slavery. In agriculture it marks the first reaping and the period of spring birth of livestock. It lasts seven days, during which one mustn’t consume or have leavened foods at home. The first two evenings the ritual dinner is made, the sèder, in which the Haggadah is read, and the liberation from slavery in Egypt is narrated. The Sivan 6th (May-June) is Shavuòt, Pentecost or "gift of the Torah". It is in memory of the consignment of the Ten Commandments to Moses on Mount Sinai. In agriculture it marks the first harvest of fruit and vegetables. The most important festival is the Sabbath. The Jews celebrate it by refraining from every working activity and dedicating the day to themselves, to their family, to study and meditation. Previously, the food for dinner is purchased, prepared and cooked, and the lamps are lighted. The Friday night meal and the Saturday lunch at noon begin with the blessing over the wine. The end of Saturday is marked by the ceremony of havdalà, "separation", which indicates the end of the holiday and the beginning of the new week.