When was the bronze age ___________
It depends on the regions and sites.
Some started early, while others started late.
From western Iran to Israel and Egypt, it started around 3200 and ended around 1100 or 1050 BCE.
In the Indian subcontinent, from 3300 to 1200 BCE.
In China, from 3100 to 300 BCE.
The Aegean civilization (Greece and western Anatolian Turkey), 3050 to 1050 BCE.
In Central Europe, from 2800 to 750 BCE.
The above dates are all approximate estimates, based on the earliest finds of bronze artifacts in those regions.
Plus the transition between Bronze Age and Iron Age are so clear-cut, because although iron may be used early, bronze might still be persistently used for centuries, depending on the availability of iron.
And some places like the cultures in the Oceanic islands and Australia, never have Bronze Age and Iron Age.
Before the 1950s, historians and archaeologists traditionally used 3000 to 1000 BCE, but contemporary define each respective Bronze Age cultures on when those regions started using bronze.
Although this may cause confusion, it is nevertheless more accurate to assign start and stop dates, dependent on the respective regions.