On 27 January 2012 10:50, Clive D.W. Feather <cl...@davros.org> wrote: > Stephen Colebourne said: >> Interestingly, in JSR-310 I may end up representing a date as a packed >> form of day-of-month (5 bits) and epoch-months (59 bits). Month >> calculations are then easy. > > Oh? When is a month from Monday coming? What day is 4 months after the last > day of next month? What about the antepenultimate day of next month? > Explain your working in each case.
Each of those three examples requires the day-of-week, thus can't be calculated from month alone (it needs the whole date). Calculating the day-of-week involves calculating a day-count, and then going from there. The point of storing data in this form is that most queries of a date are for year, month and day-of-month. Similarly, most sets/adds, like 2012-01-31 + 1month require the year, month and day-of-month. In the format above, those calculations are easy. The trade off is that some other calculations are harder. Design is always about trade-offs. Stephen _______________________________________________ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
