This means that from sunset 17 Sept 2012 untill sunset 18 Sept 2012 it was Yom Teruah, the "Day of the great awakening blast"/Feast of Trumpets as according to Torah commandment.
(Lev 23:24,25) “Speak to the children of Yisra’ĕl, saying, ‘In the seventh month, on the first day of the month, you have a rest, a remembrance of blowing of trumpets, a set-apart gathering.
‘You do no servile work, and you shall bring an offering made by fire to יהוה.’ ”
You will find a study article on Yom Teruah under the "Pages" on the right hand side of this Home page of this Blog.
This also means that another year since creation has been counted. According to the Jewish/Hillel/Rabbinic calendar count the year 5773 has been completed and this is now year 5773 and one day (on the first of Tishrei). It is an accepted fact that this count can be out with 200 and something years.
Now we have the dates for Yom ha Kippurim, Sukkot and Shemeni Atzereth too:
Yom Ha Kippurim: sunset 26 Sept 2012 untill sunset 27 Sept 2012 (10th of Seventh Month)
Sukkot starts on the evening of 1st of Oct 2012 (15th of Seventh Month) untill sunset 8th Oct 2012 (21st of Seventh Month)
Shemeni Atzeret : sunset 8 Oct untill sunset 9 Oct (22nd of Seventh Month)