Here it says that the manna ceased the day after Pesach. It started to fall on the 16th of Iyar; the Torah says that Bnei Yisrael ate it for 40 years. (Shemos 16:1,7,8,35). Were these incomplete years?
Rashi: They were full years. The dough that they took out of Egypt lasted until the 15th of Iyar; it had the taste of manna.
Why does the verse say twice that they ate from grain of the land?
Rashi: It teaches that they ate grain of the land only because the manna ceased. 1
Radak: On the 15th, they ate from old grain. Starting on the 16th, after offering the Omer, they ate from the new grain "ba'Shanah ha'Hi" (i.e. the grain of that year
Rashi: This is like a child, who says that he eats barley bread only because he has no wheat bread.
