The Rosh Chodesh of the First month, the month of the Aviv, was sighted on the evening of 13th march 2013 (5773) from Yerushalayim/Jerusalem. Since Babylonian exile, this month is also called Nisan. With this Rosh Chodesh it was the start of the new Hebrew year.
The 14th of Aviv will correspond with 27th of March.
Many of us believe that the Pesach Seder must be held on the evening of the 14th going over to the 15th of Aviv. The Seder will thus mainly be on the 15th of Aviv, the First day of Unleavened bread. The preparations for the Pesach seder will take place on the 14th of Aviv.
The First day of Chag haMatzot (15th Aviv) will correspond this year with the sunset from 27th of March until sunset at 28th of March and the whole week of Chag HaMatzot/Feast of Unleavened Bread, will be from sunset 27th of March until sunset 3 April. In other words, the last and seventh day of Unleavened bread will be from sunset 2 April until sunset 3 April. This is to be a set apart day like the First day of Chag HaMatzot.