""Rosh HaShanah is also referred to as 'Yom Teruah', the day of the Sounding of the Shofar, or the Day of the Awakening Blast. On Yom Teruah, the Day of the Sounding of the Shofar, it is imperative for every person to hear the shofar.
Yom Teruah is the only festival that no man knows the day or the hour in which it begins. This is due to the fact that it begins on the new moon. The new moon was sanctified when two witnesses see the new moon and attest to it before the Sanhedrin in the Temple. This sanctification could happen during either of two days, depending on when the witnesses come. Since no one knew when the witnesses would come, no one knew when the Feast of Trumpets would start. On the 30th of each month, the members of the High Court assembled in a courtyard in Jerusalem, where they waited to receive the testimony of two reliable witnesses. They then sanctified the new moon. Yom Teruah is the first seventh month feast falling directly on the day that the new moon is seen. It is the only feast specifically commanded by Yahweh to be kept on the new moon day. The seventh time the shofar is blown to proclaim the new moon in Yahweh's calendar is the month of Ethanin (Tishrei), the seventh month. Yom Teruah is the beginning of the count for all the seventh month moedim (appointed times). The command seems to be that we know the season, but not the day or the hour.""
http://trumpetcallofgodonline.com/images/Feast of Trumpets 9-4-10.pdf
Yom Teruah is the only festival that no man knows the day or the hour in which it begins. This is due to the fact that it begins on the new moon. The new moon was sanctified when two witnesses see the new moon and attest to it before the Sanhedrin in the Temple. This sanctification could happen during either of two days, depending on when the witnesses come. Since no one knew when the witnesses would come, no one knew when the Feast of Trumpets would start. On the 30th of each month, the members of the High Court assembled in a courtyard in Jerusalem, where they waited to receive the testimony of two reliable witnesses. They then sanctified the new moon. Yom Teruah is the first seventh month feast falling directly on the day that the new moon is seen. It is the only feast specifically commanded by Yahweh to be kept on the new moon day. The seventh time the shofar is blown to proclaim the new moon in Yahweh's calendar is the month of Ethanin (Tishrei), the seventh month. Yom Teruah is the beginning of the count for all the seventh month moedim (appointed times). The command seems to be that we know the season, but not the day or the hour.""
http://trumpetcallofgodonline.com/images/Feast of Trumpets 9-4-10.pdf