The calendar days, months, and years that we place with our articles are from the Gregorian calendar and from the Jewish calendar.
The Gregorian calendar counts the months and years from the 1st day of its 1st month, which is called "January".
The Jewish calendar calls the 1st day of the Hebrew First Month - which according to the Jewish calendar is called "Nisan" – “Biblical New Year” and counts the months from this month. The years are counted from the 1st day of the Hebrew Seventh Month - called "Tishrei/Tishri" according to the Jewish calendar. This day is called “Rosh HaShanah”. But what does the Bible call this day?
When it is the first day of the seventh month according to the Jewish calendar, which is תִּשְׁרֵי Tishrei or תִּשְׁרִי Tishri, "Rosh HaShanah" [New Year's Day] is celebrated within Judaism. It lasts for two days and in the period leading up to it, people send each other cards and emails wishing "shanah tova [a good year]." Rosh HaShanah is celebrated at home with a festive meal, which does not lack round challes and honey cake in token of a sweet, uninterrupted year. In the synagogue, the service is long (4.5 hours), and the synagogue is dressed in white. A white curtain hangs in front of the ark, where the torah scrolls are kept, and the torah scrolls are also enveloped in white robes. The chazan [cantor at Jewish prayer services] and others involved in the service wear a white linen robe, similar to the shroud used at a Jewish funeral. The white is symbolic of complete surrender to God. In the synagogue, the shofar [ram's horn] is blown 100 times, producing a sharp sound. The last tone is held as long as possible, to reflect on the coming days of repentance. These days run from Rosh HaShanah to Yom Kippur [Great Day of Atonement] in which you correct or atone for bad deeds toward other persons or toward God. The ten days end with Yom Kippur on which reconciliation with God is completed. On the eve of Rosh HaShanah, a piece of apple dipped in honey is eaten at home or in the synagogue.
If we look at the TaNaKH/Bible, we find "Yom Teruah" written on this day. This is the day when priests [not the high priest] blew silver trumpets [chatsotserot kesef] and other designated persons blew shofars and the rest of the people called/shouted to יהוה, our God, in remembrance. What we would like to know is where "Rosh HaShanah" comes from and what we can find in the Bible about it.