Hartley caught Smith off the ball in the 17th minute of the match, which Northampton went on to win 23-19.
The England hooker pleaded guilty at his hearing in London on Tuesday night and will now be free to play again on January 12.
That means he will miss Saints’ games against Harlequins, Newcastle and Sale Sharks, but will be available for the crucial Champions Cup clashes with Ospreys and Racing Metro.
Jeremy Summers, the judicial officer, heard Hartley’s case via conference call, and said: “The sanction reflects the low end entry point of the offence, which carries a two-week tariff.
“The entry point was aggravated having regard to Dylan’s previous record and a week was taken off to reflect mitigating circumstances.
“As such the sanction reflects the player’s record rather than the seriousness of the offence itself.”