The regular season is just about out of runway, which means Celtics fans can finally start doing the fun part: scoreboard-watching, matchup-guessing and mapping out the first weekend of the playoffs.

Boston already handled the big piece of business by locking up the No. 2 seed in the Eastern Conference, so the only thing left is waiting to see who comes out of the East play-in picture and lands in the Celtics’ path. As of Sunday, April 12, the NBA’s play-in tournament starts on April 14 and runs through April 17, while the first round of the playoffs opens on Saturday, April 18.

When do the NBA playoffs start for the Celtics?

The NBA playoffs officially begin on Saturday, April 18. That is the opening day of the first round for the whole league, and Boston’s series will begin either that day or on Sunday, April 19, depending on how the league finalizes the schedule after the regular season ends. The NBA has not posted the Celtics’ exact Game 1 date or tip time yet.

That part is locked in; the wait is almost over. The only thing Boston does not know yet is the opponent, because the Celtics’ first-round matchup comes from the play-in side of the bracket. With Boston locked in as the East’s No. 2 seed, they’ll face the eventual No. 7 seed.

For Celtics fans, that means the real “playoffs start” feeling may hit a few days early. Tuesday night’s East 7-vs-8 play-in game is basically the first big scouting night for Boston, because the winner of that game becomes the No. 7 seed and heads straight into a first-round series against the Celtics.

How does the play-in affect the Celtics, and who could Boston face?

The play-in tournament runs April 14-17. The format is simple:

No. 7 vs. No. 8: winner becomes the No. 7 seedNo. 9 vs. No. 10: loser is outThe loser of 7-vs-8 then plays the winner of 9-vs-10 for the No. 8 seed

Since Boston is the No. 2 seed, the Celtics will face the No. 7 seed, not the No. 8. That is an important distinction. Boston does not need to wait until the very end of the play-in to get its most likely opponent. If the East 7-vs-8 game stays on track, Celtics fans should know the first-round matchup on Tuesday, April 14.

So who looks like the most likely opponent right now? The cleanest read is Orlando or Philadelphia. The NBA’s latest bracket update showed the East 7-vs-8 matchup as Magic vs. 76ers, while Charlotte and Miami were slotted into the 9-vs-10 game. At the same time, the league also noted that the East’s seeds from 5 through 10 were still not fully settled entering the regular-season finale, with Toronto, Orlando and Philadelphia all still in the mix for the last automatic top-six playoff berth.

If the current structure holds, the Celtics’ most likely first-round opponent will be the winner of Magic vs. 76ers. If Sunday reshuffles the standings, that could change — but the Celtics are definitely waiting on the East’s No. 7 line.

What dates should Celtics fans circle for Round 1?

Here are the big dates to know:

Sunday, April 12: regular season endsTuesday, April 14: East 7-vs-8 play-in gameFriday, April 17: final play-in games for the No. 8 seedsSaturday, April 18: first round of the NBA playoffs begins

The NBA says the first-round schedule will be announced after the regular season ends. With Boston already locked into the No. 2 seed, TD Garden will be opening for playoff basketball on the first weekend of the postseason.

That is the Celtics fan version of the waiting game right now. Boston knows where it is, knows roughly when it will start and now just has to find out which play-in survivor is walking into the Garden first.