Originally Posted by
kilderkin
Many academic studies consider marks gospel to have been written within a generation or so of the approximate time of crucifixion, if not closer, it's actually considered plausible that mark writes about his own witnessing of an event in the gospel first hand when a comment about a young man running away from the events is included without any other relevant need
Either way, it is considered by many ( of course not all) to be written very close to the events it details, of course this is not a comment on accuracy
It's partly detailed in the Marcan hierarchy amongst other places