---| cdf |-----------------------------------------
mon,2,tue,4,wed,8,thu,1,fri,1

cdf[-1] = 0.0625
cdf[-2] = 0.1875
cdf[-3] = 0.25
cdf[-4] = 0.5
cdf[-5] = 1
cdf[0] = 5
cdf[1] = thu
cdf[2] = mon
cdf[3] = fri
cdf[4] = tue
cdf[5] = wed