What is the difference between the new moon of Adar 2 and Nissan?

the jewish year is a leap year this year so the order of the months goes ...adar1 adar2 nissan... there is an extra month this year.

Explanation here is brief iteration of Answer already provided on Y/A R&S (Courtesy of "Myah F") Question which asks: "Who set up the Hebrew calendar in the third century of the Common Era?" http://answers.yahoo.com/question/index;_ylt=AqxcWB1.zlm7JijwxGn0Oc8jzKIX;_ylv=3?qid=20080319194144AA3V2mE Answer cited source for "Lunisolar calendar" http://webexhibits.org/calendars/calendar-jewish.html (printed elsewhere-citation below) "About the Jewish Calendar" This year is a "Leap Year" and there is both an "Adar I" and an "Adar II" (12th month). The Torah says, "Guard the month of the spring, and make [then] the Passover offering." (Deuteronomy 16:1) Meaning, we need to ensure that Passover is celebrated in the spring. Month of Nissan is the month Passover is celebrated.