Half of the Bible is about the lives and times of the Nation of Israel. Though I do not ascribe to the belief that the ‘Hebrew’ Scriptures (Old Testament) has paramount concern for today’s faithful in comparison to the ‘New Testament’ (see my book: ‘Knowing God and Jesus, a Study in Scripture – Love, Faith and Hope’ for a more thorough examination of why Jesus fulfilled the old law), most Christian’s still cling to the idea that the old Hebrew law applies just as strongly to today’s life.
Rosh HaShanah (Hebrew: רֹאשׁ הַשָּׁנָה) is the first of the Jewish holy days and the start of the New (civil) Year. Such years begin on the first day of the lunar month Tishri (usually corresponding to the months September–October in the Gregorian calendar). The date of Rosh Hashanah was determined based on observation of the new moon. Observance of this was commanded in Leviticus. This is a two-day observance and celebration of the traditional anniversary of the creation of Adam and Eve and the start of humanity's role in God's world.
This is an important holiday to the Jewish people. The Hebrew common greeting on Rosh Hashanah is Shanah Tovah meaning ‘have a good year’. Its customs include attending synagogue services and reciting special liturgy about teshuva, as well as enjoying festive meals with family. Eating symbolic foods is now a tradition, such as apples dipped in honey, hoping to evoke a sweet new year. Many families hold a "Rosh Hashanah seder" during which blessings are recited over a variety of symbolic dishes.
I find it particularly interesting that Rosh Hashanah is not only the day of creation but is also referred to as the ‘day of judgment’. Ancient everyday Jewish life was based on a cyclical calendar, i.e. certain things always happened on certain dates. Most historian and Christian religious scholars believe Jesus’ birth was actually around this time of year also. Bibleinfo.com says ‘we can approximate the month of Jesus’ birth to be around the time of Tishri -mid to late September.’ (See their arguments here).
When you are giving the traditional Jewish greeting of Shanah Tovah, your words are filled with the meanings of creation, Jesus’ birth, and judgement time, which have or will all occur around this time of year, according to the Bible’s chronology and its cyclical calendar.