The categorization of the past into discrete, quantified named blocks of time is called periodization. This is a list of such named time periods as defined in various fields of study.
These can be divided broadly into prehistoric periods and historical periods(when written records began to be kept).
Ancient history is a time period from the beginning of writing and recorded human history through late antiquity. The span of recorded history is roughly 5,000 years, beginning with the development of Sumerian cuneiform script. Ancient history covers all continents inhabited by humans in the period 3000 BC – AD 500, ending with the expansion of Islam in late antiquity.
The three-age system periodises ancient history into the Stone Age, the Bronze Age, and the Iron Age, with recorded history usually considered to begin with the Bronze Age. The start and end of the three ages vary between world regions. In many regions the Bronze Age is generally considered to begin a few centuries prior to 3000 BC, while the end of the Iron Age varies from the early first millennium BC in some regions to the late first millennium AD in others.
The 30th century BC was a time period that lasted from the year 3000 BC to 2901 BC.