Banking calender (was: Question about floating point)
> ...Even bankers, ever counting pennies, approximate to compute interest and averages. Little known fact: sometimes they compute interest on the basis of a 360-day year.
Bankers calculate interest for 30 days per month, independent of the actual number of days, leaving 5 days of "no interest" per year. A similar practice was also seen in the Maya Haab (civil) Calendar, which has 18 months of 20 days each, plus a nineteenth "month" of 5 "bad hair days" (actually "bad luck days"). The background of the Maya Tzolkin (ritual) Calender with ist prominent bases 13 (months/year) and 20 (days/month and all multiples of years) is unclear.