Geological terms - How long ago?

Mesozoic 248m to 65m years ago Sub divided  
248 million to 206 million years ago
206 m to 144 m years
144 m to 65 m years
Cenozoic 65 m years ago to today Sub divided  
Tertiary 65 m to 1.8 m years ago Palaeocene 65 million to 55 million years ago
    Eocene 55 m 34 m
    Oligocene 34 m 24 m
    Miocene 24 m 5 m
    Pliocene 5 m 1.8 m
Quaternary 1.8m years ago to today Pleistocene 1.8 million to 10,000 years ago
    Holocene 10,000 years to today

Other terms
(Anthropological, rather than Geological terms)
Lower Paleolithic
2.5 m to 200,000 years ago. First stone tools used by hominids
Middle Paleolithic
200,000 to 40,000 years ago - Homo Sapiens using flaked stone tools.
Upper Paleolithic
40,000 to 10,000 years ago. Language thought to have developed in this time
10,000 years to when farming started around 5 - 6000 years ago
(Middle Stone age)
From the start of farming to the start of the use of metal tools, say from 5-6000 to 4000 years ago
Bronze Age
2200BC to 700BC
Iron Age
700BC to the Roman Conquest.

Want to know more? What came before the Mesozoic?