Difference between "mythology" and historical "facts"?
All we can know to be "facts" is the following: 


  Svākkhāto bhagavatā dhammo sandiṭṭhiko akāliko ehipassiko opaneyyiko
  paccattaṃ veditabbo viññūhī
  
  The teaching (of Suffering Ending Truth) well explained by the Buddha — visible in the here-&amp;-now, immediately effective, inviting inspection, leading onwards (to Nibbana), that
  sensible people can know for themselves.


This is the Dhamma Refuge taught by the Honest Awakened One (The Buddha); adhered to by Honest Noble People. This is all we can know as "fact" and this is all the Buddha expects or asks of us to know.