Since DateAndTime comment is out of date (sic !) and current implementation
seems not free of bug, here is an effort to summarize and understand the
whole thing, let's call this a review.
Please tell me where my interpretations are wrong.
1) The DateAndTime is stored internally as
- a point in UTC time (julianDayNumber, seconds, nanos)
- an offset from UTC (a Duration) denoting the local time zone
2) The ticks method returns the UTC part {julianDayNumber. seconds. nanos}
3) DateAndTime print themselves in local time using the offset
4) other methods (with some exceptions) return the local dateAndTime parts
(year month day hours minutes seconds)
Exceptions are:
- secondsSinceMidnight (which should be renamed secondsSinceMidnightUTC
IMO, even if the method is classified private)
- julianDayNumberUTC as the name tells
So far so good (but secondsSinceMidnight which is error prone)
What I find strange:
- #hash uses the offset... Why ???
d1 := DateAndTime now.
d2 := d1 offset: d1 offset + 1 hours.
{
d1 = d2.
d1 hash = d2 hash.
}
gives #(true false), a clue?
- #< compares julianDayNumber (the UTC inst. var.) with otherDate
julianDayNumber (with otherDate local offset) which seems wrong, it should
better use julianDayNumberUTC or (normalized) ticks.
- #= could be simplified and accelerated if using #hasEqualTicks: (if the
ticks are correctly normalized though which would be the case since
#ticks:offset: does, unfortunately #setJdn:seconds:nanos:offset: does not).
Some senders of #setJdn:seconds:nanos:offset: don't normalize the
day/seconds/nanos, though it should be their responsibility (DateAndTime
todayAtMilliSeconds: xxx) (DateAndTime todayAtNanoSeconds: xxx), not
counting year:month:day:hour:minute:second:nanoSecond:offset: which does
not either (many senders...).
Maybe we should better let the normalization responsibility to
#setJdn:seconds:nanos:offset:.
It remain to analyze the conversion protocol (asYear etc...) which seems to
use the local time year, but I don't understand the whole Timespan thing
right now (why DateAndTime now asYear starts now, and not on january 1st?).
Nicolas
