Cultural Levels in Domains of Dread denotes the technological level though with regards to Iron and Classicl there really isn't that much difference as far as technology goes
|Stone Age||10000-5000 BCE||TL0||Prehistory and later|
|Bronze Age||5000-2500 BCE||TL1||3500 BCE+|
|Iron Age||2500-1 BCE||TL2||1200 BCE+|
|"Classical"||1-500 CE||TL2||1200 BCE+|
|Dark Age||500-800 CE||TL3||600 CE+|
|Early Medieval||800-1200 CE||TL3||600 CE+|
|Medieval||1200-1400 CE||TL3||600 CE+|
|Chivalric||1400-1550 CE||TL3 to TL4||600 CE+; 1450+|
|Renaissance||1550-1700 CE||TL4 to TL5||1450+; 1730+|
|"Masque of the Red Death"
GURPS Tech Levels have been added to make use of this setting outside of games like D&D easier.
It should be noted what the Domains of Dread called "Iron Age" is set about 1300 years earlier than it actually occurred (ca 1300 BCE). Contrary to what the book said, while rare, locks, keyes, and metal armor existed in the historical Bronze Age.
"Classical" generally refers the period 8th century BCE and the 6th century CE centered on the Mediterranean Sea so here again the time period is "off". Also research has shown that pre-collapse Bronze Age cultures were as, if more, sophisticated as those in the classical period.
The very term Dark Age has been largely thrown out and replaced with "Early Middle Ages" (c 500 to c 1000 CE) with High Middle Ages (c 1000 to c 1250) and Late Middle Ages (c 1250 to c 1500) used to describe the rest of the period.