Comparative dates on which the Nationals notched their 15th win, each season:
2005 - 4th May (28th match of season)
2010 - 6th May (28th match)
2011 - 6th May (32nd match)
2008 - 8th May (35th match)
2007 - 17th May (41st match)
2006 - 20th May (43rd match)
2009 - 2nd June (51st match)