A list of the main archaeological periods covered by each of biab's classification numbers (2-9) with an indication of the approximate span of each period in calendar years. These dates should not be taken as definitive or absolute and may well be debated; however, users may appreciate a more explicit guide to the chronological framework against which bibliographic references are classified.

1. GENERAL, MULTI-PERIOD or UNDATED [classification code 1]
   
2. PALAEOLITHIC & MESOLITHIC [classification code 2]
   • Palaeolithic (Pal) 500,000BC-10,000BC
     • Lower Palaeolithic 500,000BC-70,000BC
     • Middle Palaeolithic 70,000BC-35,000BC
     • Upper Palaeolithic 35,000BC-10,000BC
     • Early Upper Palaeolithic 35,000BC-20,000BC
     • [Last Glacial 23,000BC-15,000BC]
     • Late Upper Palaeolithic 15,000BC-10,000BC
   • Mesolithic (Meso) 10,000BC-4000BC
     • Earlier Mesolithic 10,000BC-8000BC
     • Later Mesolithic 8000BC-4000BC
3. NEOLITHIC [classification code 3]
   • Neolithic (Neo) 4000BC-2300BC
     • Early Neolithic 4000BC-3400BC
     • Later Neolithic 3400BC-2300BC
4. BRONZE AGE [classification code 4]
   • Bronze Age (BA) 2300BC-700BC
     • Early Bronze Age (EBA) 2300BC-1200BC
     • Middle Bronze Age (MBA) [2000BC-1500BC (Mid E dates)]
     • Late Bronze Age (LBA) 1200BC-700BC
5. IRON AGE [classification code 5]
   • Iron Age (IA) [Lowland Britain] 700BC-AD43
     • Early Iron Age (EIA) 700BC-400BC
     • Middle Iron Age (MIA) 400BC-100BC
     • Late Iron Age (LIA) 100BC-AD43
   • Iron Age (IA) [Ireland & N Scotland] 700BC-AD450
     • Early Iron Age (EIA) 700BC-400BC
     • Middle Iron Age (MIA) 400BC-100BC
     • Late Iron Age (LIA) 100BC-AD450
6. ROMAN BRITAIN [classification code 6]
   • Romano-British (RB) [Lowland Britain] AD43-AD450
7. MIGRATION & EARLY MEDIEVAL [classification code 7]
   • Migration & Early Medieval (MEM) AD450-1066
   • MEM [Ireland] AD450-1170
   • Anglo-Saxon (AS) AD450-1066
8. MEDIEVAL [classification code 8]
   • medieval (med) 1066-1547
   • medieval (med) [Ireland] 1170-1547
9. POST-MEDIEVAL, INDUSTRIAL, RECENT [classification code 9]
   • post-medieval (post-med) 1547-
   • Industrial (Ind) 1700-
   • modern (mod) 1901-