Contradiction with Matthew 26:73
In Matthew, others recognize Peter by his speech, suggesting a different reason for suspicion than time alone.
Matthew 26:73: Then began he to curse and to swear, [saying], I know not the man. And immediately the cock crew.
Contradiction with Mark 14:70
Similar to Matthew, Mark notes Peter's Galilean accent as the giveaway, rather than the time elapsed.
Mark 14:70: And he denied it again. And a little after, they that stood by said again to Peter, Surely thou art [one] of them: for thou art a Galilaean, and thy speech agreeth [thereto].