We're all pretty familiar with the snowless winter of 1972-1973 -- the only winter where Philadelphia did not pick up any measurable snowfall at the Airport -- lots of trace amounts that winter but no single storm to bring more than that. Thanks to December 1973 bringing 4.6" of snow, 1973 finished with more snow than this past calendar year.
2012 ended up tied for the fourth least snow in Philadelphia over the course of January-December since snow was first recorded in 1884. The only years with less snowfall was 1913 (1.7"), 1998 (2.0"), and 1931 (3.2").
The common denominator in 1931 and 1998 are that both years were historically warm even in our times -- like 2012, which surpassed both of these years in warmth. 1913, which isn't one of the warmest years when you add recent times into the mix, was historically warm for its time, finishing 2.7 degrees above the average temperature of the era and had been the warmest year on record to that point.
What made 1913 a bit more intriguing was that the winter of 1913-1914 finished with over 33" of snow -- over 30" of which fell between February and March. They went from snowless to snowy in relatively short time. While it may be a bit less likely that we get such similar results -- getting 15" of snow in March only happened that one time -- it does show just how fickle these snowy results (or snowless results) can be.