Give some stream of consciousness and then the answer. The Milwaukee Brewers' 1998 season was the first season for the franchise as a member of the National League. The Brewers finished in fifth in the NL Central, 28 games behind the Houston Astros, with a record of 74 wins and 88 losses. Before the 1998 regular season began, two new teams -- the Arizona Diamondbacks and Tampa Bay Devil Rays -- were added by Major League Baseball. This resulted in the American League and National League having fifteen teams. However, in order for MLB officials to continue primarily intraleague play, both leagues would need to carry a number of teams that was divisible by two, so the decision was made to move one club from the AL Central to the NL Central.

Answer this question: when did milwaukee brewers move to the nl?
This is the relevant information: The Milwaukee Brewers' 1998 season was the first season for the franchise as a member of the National League.
Therefore, the answer is 1998.