One effect of the promise of Jesus to come again in glory during the
lifetime of some of his hearers is to date the gospel without the aid
of any scholarship. It must have been written during the lifetime of
Jesus's contemporaries: that is, whilst it was still possible for the
promise of his Second Coming to be fulfilled. The death of the last
person who had been alive when Jesus said "There be some of them that
stand here that shall in no wise taste death till they see the Son
of Man coming in his kingdom" destroyed the last possibility of the
promised Second Coming, and bore out the incredulity of Pilate and the
Jews. And as Matthew writes as one believing in that Second Coming,
and in fact left his story unfinished to be ended by it, he must have
produced his gospel within a lifetime of the crucifixion. Also, he must
have believed that reading books would be one of the pleasures of the
kingdom of heaven on earth.