July 2215 BCE
- The comet Hale-Bopp passes within 1.4 AU1 of Earth. Hale-Bopp returned recently in 1997. The next pass of Hale-Bopp into the inner solar system will be c. 4385.2
c. 2100 BCE
- Earliest known calendar. The Umma Calendar of Shulgi ( Babylonian) was a lunisolar calendar with years consisting of 12 lunar months.
c. 2000 BCE
- The Egyptian Royal Courier system begins for the elite in Egypt. Messages were passed from courier to courier and would travel to the most distant parts of the empire.
- Mesopotamians could solve Quadratic Equations.
- Stonehenge is believed to have been completed.
- Glassworking appears.
- The last woolly mammoth goes extinct on Wrangel Island.
- It would be 3990 years before the release of Lemmings.