Comparative dates on which the Nationals notched their 18th win, each season:
2012 - 5th May (27th match of season)
2014 - 6th May (32nd match)
2013 - 8th May (33rd match)
2005 - 9th May (32nd match)
2010 - 10th May (32nd match)
2011 - 11th May (36th match)
2008 - 15th May (42nd match)
2007 - 24th May (47th match)
2006 - 24th May (47th match)
2009 - 17th June (64th match)