On 14/11/13 17:48, Jürgen Hestermann wrote: > Am 2013-11-14 07:56, schrieb Patrick Chevalley: [...] > >> The julian year of 365.25 is a convenient approximation still in >> use despite the julian calendar was abrogated some 400 years ago. > > Of what use would it be to use 365.25 days as a representation of a > year? You can also use 400 instead. It would be just an arbitrary > definition decoupled from calendars. You cannot calculate anything > useful with it. Neither calendar dates nor astronomical things. It is > just an accademic value and exists only because it is "so easy to > use". >
You know what they say about statistics: there are lies, big lies and there is statistics. Statistics only works if you have large enough data set to calculate the model from... (and /similarly/ or same large data set to extrapolate from, thereafter) (http://en.wikipedia.org/wiki/Gregorian_calendar is a fascinating read :] ) And for what it's worth, the fraction-based calculations should be then far less [time...] consuming, to just add/subtract/multiply/divide the fractions, than counting the days/hours/mintues/secods one by one... (Only, it needs to be done right :> and the leap year/leap month/30-31day exceptions observed when it comes to the dates: 1 day is at least 0.00273790700 of an average year as in 1/365.2425 - keep too little of this fraction or even worse: corrupt it, and you're in for a bad result...) Problems may arise with improper rounding up or down, and floating point bugs (assuming the fraction part of TDateTime to be miliseconds / MilisecondsPerDay : Pentium FPU anybody?) On the other hand if the calculations were Gregorian year based (365.2425...) it'll now be good enough for calculating all western calendar dates since 15/10/1582 :) and to some extent, predict into next century or so. -L :) -- _______________________________________________ Lazarus mailing list [email protected] http://lists.lazarus.freepascal.org/mailman/listinfo/lazarus
