It happens in baseball on occasion. That's why I'm asking. I wasn't sure if it's ever happened in the NHL or if it could happen
You're right - a year or two ago, the Indians played a 161 game season instead of 162 games. I forget the other team, but it was a game that wouldn't change seeding or entry into the post season.
If there were a disaster that struck really, really close to the end of the season, and a team involved played on the final Friday AND the final Saturday, then yeah, they might schedule a conditional game on Monday, because that's cutting into the post-season, and doesn't give ticket holders a good chance to either rearrange their lives or sell their tickets.
In this case, AFAIK, the Bruins didn't offer refunds, although they'd probably gladly have taken the tickets off anyone's hands. The weekday January game was going as low as $50 or $60 IIRC. The Sunday regular season ending game is now going for about $140 on the official exchange. There's 2-3 months to figure out what to do with the tickets, and selling them at a profit would be easy for most people to do if they couldn't go...or they could go to a game that's "better" - end of the season, and now on a weekend.
In short, JJ wants his beer money, and rescheduling the game gets him that. It doesn't put too much stress on the teams, as the NHL has a moderately lengthy break compared to the MLB, resting for three days. I think baseball almost immediately goes into any tie breaker games on the Monday after the regular season , followed by wild cards on Tuesday and Wednesday, with 2 of the ALDS and/or NLDS series starting Thursday.
Plus, the Bruins are likely to get an extra day of rest, since the Celtics play at home on Wednesday.