The pass of time

Hi.

It is correct to say;

The time passed quickly. we didn't understand the pass of time.

what is the correct expression in that case.

For instance, I and my friend were talking for a while, then we realized that we had been talking for three hours.

Then I said, The time passed quickly, we didn't understand the pass of time.

I would appreciate if you could tell me what native speakers say in the occation I cited.

Thanks