Since the 2013 season, the 20 interleague games are played in eight series. Each team plays one three-game series against four teams from one division in the other league, and two two-game series (one home, one away) against the remaining team in that division. Divisions have been rotated since 2002 but teams did not necessarily play everyone in that division prior to 2013. The remaining four games are played against a team's "natural rival" in home and home two-game series. From 2013 to 2017 these two series were back-to-back at one venue on Monday and Tuesday and at the other team's venue that Wednesday and Thursday. Should a team's natural rival be a member of the division they are scheduled to play as part of the yearly rotation (this first occurred for all teams in 2015), the team will play home-and-home three game series against the natural rival, home-and-home two game series against two other opponents, and single three game series against the last two (one home, one away). For 2013, all natural rivalry games were played May 27–30. Teams played at one park on May 27 and 28, then traveled to the other team's park for games on May 29 and 30. For 2014, 2016, and 2017, these games were spread out throughout the season, ranging from the second week of the season in April through mid-August. Because the requirement for nearly daily interleague play (the only exception being if not all teams are playing) spreads out interleague play throughout the year, not every team will be in interleague play on the same day. Due to the new CBA lengthening the schedule by four days, 2018 was the first year during which no team was required to play back-to-back home-and-home two game series against any other team.