When were the Gospels Written?
Most of the Gospels are believed to be written potentially as early as 10 years after the death of Jesus to anywhere up to 30-40 years after his death (here’s a great article about reasons to assume an earlier date for the gospels). It is believed that Mark is the earliest Gospel and that Matthew & Luke used Mark as a primary source to help guide their writing. Because of this fact, Matthew, Mark, and Luke are called Synoptic Gospels by some. John’s gospel tends to focus on different aspects of the ministry of Jesus’ ministry than the other three and stands alone as a theological treatise on the work of Jesus.
Can we really trust these documents if they were written after so much time had elapsed?
Yes, 100%. Early Christians believed Jesus would return in their lifetime. As the first Christians and eyewitnesses grew older they began to realize they wouldn’t be around to convey the story of Jesus and so they wrote down the things they had already been preaching for years to the church in an oral manner. Since the very beginning of the church (see Acts 2:42) these leaders had been telling the stories of Jesus repeatedly and it would not have been hard for them to write them down.
As a side note, when humans experience something life-altering we tend to have an incredible ability to recall those experiences later in life, sometimes with photographic like recall (think the birth of a child, the loss of a loved one, moments on a battlefield for a soldier). Now imagine you are seeing things like the healing of lame people, or the blind, or seeing someone flip over tables in a temple, or hearing them teach ideas you had never been exposed to. There is a very strong likelyhood those events would be burned into your memory for the rest of your life.
Aside from that, the whole job of a disciple was to learn to be exactly like their rabbi – to learn how they talked, thought, and what they taught. Jesus’ disciples would have been no different. They spent three years studying every move Jesus made and were even sent out on a couple missions to practice teaching and living out the way Jesus lived.
It’s also important to note that the earliest records we have from the Christian community (people living 60-70 years after Jesus) accepted these four Gospels as the accurate eyewitness accounts of the live and ministry of Jesus.
Trust it, 100%!