What is the Yashan cutoff date for Heckers flour?
From Y. Herman's Guide to Chodosh (5776):
Heckers white flour contains 100% winter wheat, as determined by independent sources. Probable Chodosh date for malt is Dec 15, code best by use date of June 15 17 (18 months after packing.)
Some people are not strict about malt, in which case the white flour is always Yoshon (since winter wheat in the United States is always planted well before Pesach yet doesn't hit store shelves till after).
With regard to Hecker's whole wheat flour:
Heckers whole wheat flour Chodosh code Aug 2 16 (1 year after packing.)