I was told in school that the gospels were written hundreds of years after the fact, by individuals who not only had not witnessed the incidents, but had not personally known any witnesses.
It was only years later that I learned that:
- Luke and Acts were written by the same author, as parts of a single narrative, and
- Mark was written before Luke, and
- Acts doesn't mention the deaths of Peter and Paul, around 65AD, or the destruction of the Temple in 70AD. Which they certainly would have, had they been written after those dates.
In other words, Luke was written less than 30 years after the crucifixion, and Mark was written earlier than that.