A        Annually (Calendar Year)
C        Daily
D        Discrete
F        Flexible Interval (from Date X through Date Y)
M        Monthly Bucket (Calendar Months)
Q        Quarterly (Calendar Quarters)
S        Semi-Annually (Calendar Year)
T        Four week bucket (13 buckets per year)
W        Weekly Bucket (Monday through Sunday)
X        Weekly Bucket (7 day interval)
Z        Mutually Defined