When To Stop Eating/Possessing Chametz

After the fourth halachic hour on the eve of Passover:
  • You may not eat chametz or kitniyot.
  • You may not eat non-chametz food cooked in a chametz utensil. 
By the fifth halachic hour on the eve of Passover:
The chametz must be burned.
Note A halachic hour is a local daytime hour calculated by dividing the total number of daylight hours by 12.