Each regular season has a 160 game schedule spread out from April 1st to September 29th. In a new league, the seasons usually start at the year 1990 and go on from there.
Structure of a Season
A team will play a series of games against various teams during the course of a season. The schedule is structured in a way that you play an entire division at the same time before playing another division or conference. For example, if my team is part of the AL East then I would open up the season against all AL East teams, then play AL West teams, then back to AL East teams, etc.
The breakdown of how a series and schedule is constructed is below:
In-Division Matchups:
The team your facing is one of 5 other teams in your division.
You open the season and close the season playing teams in your division.
Each series against a team in your division is either 3 or 4 games long.
A 3 game series against a team in your division happens twice a season (6 total games)
A 4 game series against a team in your division happens twice a season (8 total games)
You face each team in your division a total of 14 times (6 + 8) apiece per season.
You play a total of 70 in-division games per season.
Conference Matchups:
A conference opponent is one of 6 teams from the other division that makes up your conference.
Each series against a team is always 3 games.
You face a team from your conference a total of 3 times per season.
You play a total of 9 games per season against each conference team.
You play a total of 54 conference games per season.
Interleague Matchups:
An interleague opponent is a team who is in the other conference that makes up your league.
For roughly 1 1/2 months during the end of June and all of July teams will participate in interleague play against the other conference.
Each team will play a total of 3 games per interleague matchup, for 1 series per season.
Each team faces all 12 teams in the other conference.