(Hebrew: / Spelling: Rosh Hashana, Rosh Hashanah / Other Names: Yom Zicaron, Day of Remembrance, Yom Tiruah, Day of Trumpeting, Yoma Arichta / Definition: Jewish New Years day.)
New Years day on the Jewish Calendar. On Rosh Hashana all judged in front of Hashem and their fate is decided for the upcoming year.
Four Rosh Hashana's
Although the term Rosh Hashana is generally used to refers to the Jewish New Year's that falls out on the first of Tishrei the Mishanh list four different Rosh Hashana's or beginning days. On the first day of Tishray it is Rosh Hashanah for the Years, Shmitah, Yovlim, Planting and Vegetables.
Years - It is the first day of the Jewish Calender and is used for dating documents. Additionally the human race is judged on this Rosh Hashana for the upcoming year.
Shmitos and Yovlim - Once Rosh Hashana comes in it becomes forbidden to plow the land Mdioraysa on every seventh and fiftieth year of the Shmitah cycle.
Planting - In reference to the three years a tree needs to get out of its Urlah status, Rosh Hashana is considered the starting point. Even if a tree was planted 45 days earlier during the month of Av, when Rosh Hashanah comes around it is already considered the second year.
Vegetables - It is forbidden to give Masser from vegetables that grew in one year from vegetables that grew in a previous or later year. Rosh Hashanah is the determining point that establishes the year for vegetable Masser. Therefore one would not be able to give Masser from vegetables that were harvested on Erev Rosh Hashana from vegetables that were harvested the day after Rosh Hashanah.
Day of Judgment
Rosh Hashana is a day of Remembrance in front of Hashem. On this day He remembers all creations and judges them; who will live, who will die, who will become rich and who will become poor etc. Hashem looks over the hearts of all creations all in one glance but at the same time perceives each creation individually.
Aside from individuals, nations are also judged as a whole on Rosh Hashanah; which land will have prosperity, which land will have famine, which land will have war and which land will have peace.
The Three Books
On Rosh Hashana, three books are opened in the heavenly court. Completely Righteous people are written in the Book of Life. Completely Evil are sealed for death. Everyone else in between have their final judgment delayed until Yom Kippor so they have a longer chance to repent.
Two Day Yom Tov
Rosh Hashana is the only holiday that is observed for two days, even in Eretz Yisroel. Unlike the other two day holidays in Diaspora, these two days are considered one joint holiday and are called 'Yoma Arichta' (a long day). This causes a number of differences in Halacha.
Establishment of a Two Day Holiday
Rosh Hashanah is the only holiday that falls out on Rosh Chodesh. During the times of the second Bais Hamikdash and before the establishment of a set Jewish calendar, each Rosh Chodesh was established at the sighting of the new moon. Each month there is a frame of two days during which exists a possibility for the birth of the new moon to appear. When the new moon was sighted, witnesses would travel to the Sanhedrin, testify and Rosh Chodesh would be announced. Many times the witness would only arrive during the day time, which meant the night before was retroactively holy.
This led to two issues. Firstly if the witnesses would arrive on either of the two possible days during later hours, It would mean the holiday of Rosh Hashana had already started the night before.
(In the case of Rosh Hashanah, if witnesses were to arrive during the day time of 'Alef Tishrei', it would mean the Holiday had already begun from the night before. In order to avoid the possibility of desecrating Rosh Hashana, Bais Din and the nation would start observing the holiday from night leading to Alef Tishrei.
Some years however, witnesses of the new moon would not arrive until the second day, meaning 'Alef Tishrei' was a regular day and was really the last day of Elul.)
Although Rosh Hashana is considered a holiday, the Hallel is not recited. Due to the tremendous awe and trepidation of this day when people are judged for life and death, it is not appropriate to sing the Hallel.