The 'Dark Ages' started when the Roman army left Britain and finished when the Saxons ruled the whole of England. From about AD 410 to AD 710. This was the time when the British were ruling by themselves without Roman help. The Saxons were fighting them and taking over parts of the country. The Scots were fighting the Picts and taking over parts of the country too. This period of history is called 'Dark' because, in the past, historians knew very little about it. They couldn't see any information in the darkness!  We now know lots about this period of history. So some historians don't like the term 'Dark Ages' any more. Some people call it 'Post-Roman' or 'Sub-Roman' times. The Romans did not reach some parts of Britain though. So some people call this period 'Late Celtic' or 'Early Christian' times instead. Some people forget about the Romano-British, the Scots & the Picts and just call it 'Early Saxon' times. These terms all mean the same thing. In England, the Dark Ages were followed by Middle & Late Saxon Times. In Scotland and Wales, this was just called the Early Medieval Period.