Just a random thought, looking at my excel spreadsheet on days I've gone hiking, I've not gone hiking on my wife's birthday, my mother-in-laws birthday or my daughter's birthday, ever, even before I was married or before my daughter was born.
Other oddities, most days together I have hiked is 10 (not the same year - 2x) although some eight & seven day stretches are only separated by one day. From 10/6 to 10/16, I've hiked every even day & off every odd day. I have yet to hike from May 2nd to May 12th, the longest stretch.
The day I've hiked the most on? 8/13 (1992, 1994, 1995, 2010 & 2011 - 11 days 4X) 8/13 is my parents (long since divorced) Anniversary.