From their press release:
After leading the NBA with 18 road contests through this point of the 2020-21 season, Boston is slated to play 19 games at TD Garden during the season’s second half. Eleven of those 19 home contests are scheduled in the month of April, with a season-long seven-game homestand – featuring marquee matchups against the Dallas Mavericks (March 31) and Philadelphia 76ers (April 6) – occurring from March 29 through April 9. The Celtics will play host to the Charlotte Hornets on April 4, marking Gordon Hayward’s first game back at TD Garden after spending the past three seasons with Boston from 2017-18 through 2019-20.
Out of Boston’s five road games scheduled during the home-heavy month of April, four will come against teams currently boasting a top-10 winning percentage in the Denver Nuggets (April 11), Portland Trail Blazers (April 13), Los Angeles Lakers (April 15), and Nets (April 23). The Celtics will be on the road for five of their final eight games, including a three-game road trip to close out the regular season.
In addition, the Celtics have long road trips near the end of March and in the middle of April.
Note that the trade deadline is on March 25th which is sandwiched between two road games against Milwaukee (on the 24th and 26th).