At 0:11 of the second period in the Penguins/Senators game, Pittsburgh requested a Coach's Challenge to review whether Zack Smith was off-side prior to his goal.
After reviewing all available replays and consulting with the Linesman, the Situation Room determined that Smith was off-side prior to the goal. According to Rule 78.7, "The standard for overturning the call in the event of a 'GOAL' call on the ice is that the Toronto Video Room, after reviewing any and all available replays and consulting with the Linesman, determines that one or more Players on the attacking team preceded the puck into the attacking zone prior to the goal being scored and that, as a result, the play should have been stopped for an "Off-side" infraction; where this standard is met, the goal will be disallowed."
Therefore, the original call is overturned - no goal Ottawa Senators.
The clock is re-set to show 19:56 (0:04 elapsed time), when the off-side infraction occurred.