Here is some info you might find helpful:
Traditional
Opening Day, featuring all 30 Major League Clubs, will take place on Thursday, March 28th. The
2019 season will mark the second
season under the scheduling format agreed to as part of the
2017-2021 Basic Agreement between
MLB and the Major League
Baseball Players Association (MLBPA).
The 2018 Major League Baseball regular season will open on the earliest day ever (excluding international events) on Thursday, March 29, and will feature every team playing on the same day.
It's the first full slate of games since 1968.
and from Wikipedia:
"Opening Day is the day on which professional
baseball leagues begin their
regular season. For
Major League Baseball and most of the
minor leagues, this day typically falls during the first week of April, although in recent years it has fallen in the last week of March. In
Nippon Professional Baseball, this day typically falls in the last week of March.
For baseball fans, Opening Day serves as a symbol of rebirth; writer
Thomas Boswell once penned a book titled,
Why Time Begins on Opening Day.
[1] Many feel that the occasion represents a newness or a chance to forget last season, in that all 30 of the major league clubs and their millions of fans begin with 0–0 records.
[1]
Opening Day festivities extend throughout the sport of baseball, from hundreds of
Minor League Baseball franchises to
college, high school, and youth leagues in North America and beyond. Since
Major League Baseball generally starts their season first among professional leagues, their Opening Day is the one most commonly recognized by the general public. Most of the minor leagues start a few days later, but within the same week; the
short season Class A and Rookie leagues are exceptions, since they begin play in June. (College, high school and youth baseball seasons vary widely depending on location and weather conditions.) Opening Day ignores the
exhibition games played during
spring training in the month leading up to Opening Day."
You can extrapolate closing day of the exhibition season from this.
Richard