Egypt was one of the Earth nations visited by the alien being Kukulkan in the ancient past. The alien creature influenced Egyptian architecture and agricultural development. Kukulkan told the Egyptians to build a city with pyramids and obelisks. When the city was finished, Kukulkan was supposed to return. The Egyptians only finished parts of the city, and did not complete the energy amplification system that was supposed to signal Kukulkan. (TAS: "How Sharper Than a Serpent's Tooth")
The Kukulkan visit was not given a specific date but the accounts would seem to suggest an era around 5,000 BC to 2,000 BC.
Temporal researchers would observe the building of the pyramids in Egypt. This would be visible on Daniels' temporal observatory. (ENT: "Cold Front")