Comparative dates on which the Nationals clinched their 18th win, each season:
2005 - 9th May (32nd match of season)
2010 - 10th May (32nd match)
2011 - 11th May (36th match)
2008 - 15th May (42nd match)
2007 - 23rd May (47th match)
2006 - 24th May (47th match)
2009 - 17th June (64th match)