I ate pizza yesterday.

I eat pizza everyday.

I will eat pizza tomorrow.

I was eating pizza when you arrived.

I am eating pizza right now.

I will be eating pizza when you arrive.

I had eaten all of the pizza when you arrived.

I have eaten all of the pizza.

I will have eaten all of the pizza by the time you arrive.

I had been eating pizza for 2 hours when you arrived.

I have been eating pizza for 2 hours.

I will have been eating pizza for  2 hours when you arrive.