External Evidence
nMatthew was written before the earliest surviving manuscripts of it.
nP64,67 and p77 come from ~200.
nPseudo-Barnabas (~132) cites Matt 22:14.
nTradition on authorship would place it before Matthew’s death, so probably well before AD 100.
nIrenaeus’ tradition would put it 61-68.
nOther traditions put Matthew first, so perhaps even earlier.