Hi Rooters,
I have a problem in deciding if TDatime is a useful class for me. I have
seen that there was already a thread concerning a similar issue in this
mailing list (http://root.cern.ch/root/roottalk/roottalk01/4470.html),
but the problem is not yet fixed (for me).
As far as I understood the TDatime.cxx code, the internal representation
in TDatime is related to the date/time in the local time. If one wants to
exchange data to another time zone (in our case from Argentina (GMT+3) to
GMT-6 .. GMT+2), even the method Convert(kTRUE) does not give the right
result, as one has to know always both timezones (?). Wouldn't it be
better to use the UTC value (possibly shifted by an offset 1970 ->
1995) for the internal representation ?
Or is it better to follow from the beginning the approach of R. Hatcher
(http://root.cern.ch/root/roottalk/roottalk01/4474.html) prior to extend
the class TDatime into TNanoDatime ?
The next confusing point and probably pure academic is that time() doesn't
return the UTC time, as UTC is officially defined to be the real number of
seconds since 1.1.1970 UT, INCLUDING the leap seconds which are (according
to my man-pages, might be wrong) not taken into account in a standard
(Posix conform implementation) of the time() function.
Quoting from the man-page:
time returns the time since the Epoch (00:00:00 UTC, January 1, 1970),
measured in seconds.
POSIX.1 defines seconds since the Epoch as a value to be
interpreted as the number of seconds between a specified
time and the Epoch, according to a formula for conversion
from UTC equivalent to conversion on the naive basis that
leap seconds are ignored and all years divisible by 4 are
leap years.
...
The intention is
that the interpretation of seconds since the Epoch values
be consistent; see POSIX.1 Annex B 2.2.2 for further
rationale.
---- end of quote
Regards and thanks for clarification
Hermann-Josef
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