In the Old Testament, the Feast of Trumpets was observed on the first day of the seventh month, which after the Babylonian exile was called "the first of Tishri." The original practice of identifying the months by their numerical order was eventually abandoned in favor of the Babylonian names of the month. Thus "the first day of the seventh month" became known as "the first day of Tishri." Since Tishri was the first month in the Babylonian calendar, the Jews called the first day of Tishri Rosh Hashanah, literally meaning "Head of the Year." The Jews still observe Rosh Hashanah as their New Year which marks the beginning of what is alternatively called the "Ten Days of Repentance," or the "Days of Awe." These are the ten days of introspection and preparation for the Day of Atonment (Yom Kippur), which falls on the tenth day of the seventh month.

http://www.biblicalperspectives.com/books/festivals_2/2.html

I know many are looking to September 13th (Rosh Hashanah) as a potential day for some type of disaster or collapse. 10 days following that is Yom Kippur on Sept. 23, 2015. Just an interesting correlation. Maybe we are given 10 days to repent after the warning?