The halacha concerning yoshon is complex. Here are links to further reading.

1. Wikipedia: http://en.wikipedia.org:80/wiki/Yoshon



2. What is "Yoshon"?:
   http://www.kosherconsumer.org/yoshon.htm



3. Yoshon and Chodosh - Something Old Something New:
   http://www.star-k.org/kashrus/kk-yoshon-old_new.htm



4. Practically Speaking: A Housewife's Perspective on Keeping Yoshon:
   http://www.star-k.org/kashrus/kk-yoshon-prepyoshon.htm



5. The Orthodox Union and Its New Yoshon Supervision: http://www.ou.org/kosher/daf/advanced/yoshen.htm

The items shown below do not indicate the chodosh or yoshon status of the grain product. They indicate that the product which may contain chometz was not manufactured during the days of Pesach in the specified year. The terms noch pesach [Yiddish] or l'achar pesach [Hebrew] may be used instead of after Pesach.