At 1:38 of the second period in the Stars/Sabres game, Buffalo requested a Coach's Challenge to determine whether Dallas was off-side prior to their goal.
After reviewing all available replays and consulting with the linesmen, NHL Hockey Operations staff determined that Dallas' Patrick Eaves 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 Dallas Stars.
The clock is re-set to show 18:31 (1:29 elapsed time), when the off-side infraction occurred.
Since the Coach's Challenge resulted in the original call being overturned, the Buffalo Sabres retain their time-out.