going on several road series in a row. Teams generally play games five to seven days per week. Most games are scheduled at night, although teams will often play day games on Opening Day, holidays, and for the last game of a series to allow teams extra time to travel to their next opponent. Sunday games are generally played during the afternoon, allowing teams to travel to their next destination prior to a Monday night game. In the current three-division structure, each team plays 19 games against each of its four divisional opponents. It plays one home series and one away series, amounting to six or seven games, against the 10 other teams in its league. A team also plays one of the divisions in the other league, rotating each year, with two opponents in a three-game home series, two in a three-game away series, and one with four games split between home and away. Furthermore, each team has an interleague "natural rival" (in many cases its counterpart in the same metro area) with which it plays two home games and two away games each year. With an odd number of teams in each league (15), it is necessary to have two teams participate in interleague play for most days in the season, except when two or more teams have a day off. Each team plays 20 interleague games throughout the season, usually with just one interleague game per day, but for one weekend in late May, all teams will participate in an interleague series. Before 2013, interleague play was structured differently: there would be one weekend in mid-May and another period consisting typically of the last two-thirds of June in which all teams played interleague games (save for two NL teams each day), and no interleague games were scheduled outside those dates. (Before 2013, season-long interleague play was not necessary, because each league had an even number of teams. In 2013, the Houston Astros moved to the American League, so that each league would have 15 teams.) Prior to the adoption of the universal designated hitter in 2022, whether the DH was in use depended on whether the home team was from the AL, where the DH was used, or the NL, where it was not. Starting with the 2023 season, the scheduling formula is set to change, with each team playing at least one series against every other