On April 23, 2008, against the Colorado Rockies, the Cubs recorded the 10,000th regular-season win in their franchise's history dating back to the beginning of the National League in 1876. The Cubs reached the milestone with an overall National League record of 10,000-9,465. Chicago was only the second club in Major League Baseball history to attain this milestone, the first having been the San Francisco Giants in mid-season 2005. The Cubs, however, hold the mark for victories for a team in a single city. The Chicago club's 77–77 record in the National Association (1871, 1874–1875) is not included in MLB record keeping. Post-season series are also not included in the totals. To honor the milestone, the Cubs flew an extra white flag displaying "10,000" in blue, along with the customary "W" flag.

When did the Cubs record their 10,000 regular-season win?