You may have to get a bit more specific in your terms. There are hundreds of pyramids in Egypt, not just the ones at Giza. To which Pyramids are you referring?

You may have to give consideration to the terms "always" and "common knowledge". People living in Britain or Japan probably didn't hear of them for many, many years after their completion, and people living in the Americas probably didn't hear about them until the Fifteenth or Sixteenth Centuries.

A better way to word your question would be like this: How quickly through Europe, Asia, and Africa did knowledge of the Pyramids at Giza spread? Was this knowledge limited to trading caravans and soldiers, who would have seen them in person, or was the knowledge available to other people, as well, like scholars and nobles?