The Iron Age.
( What has gone before. )
1500 BCE. Iron is Smelted in Armenia.
1400 BCE. The Hittites beat the Iron into something useful.
1200 BCE. Iron is now so useful we call this the start of the “Iron Age”
700 BCE. The Greeks call the tribes of Central Europe the “Keltoi” or “Celts”.
( What we called them is not recorded. )
450 BCE. The British finally catch up with everybody else and join the “Iron Age”.
( For more details and less flippancy see the Chronology. )