On Mon, Jul 13, 2009 at 11:28 PM, Marnen
Laibow-Koser[email protected] wrote:
Yes – wherever you happen to be. Not in some other time zone.
I know Time.new’s syntax is not like this – just trying for clarity.
A clock time cannot be a useful without a time zone – even if that time
zone is set to a sensible default, it’s still there.
But there are definitely use cases where the time zone is NOT
inherently part of the time value.
I’ve spent quite a bit of time looking at things like this in
implementing ri_cal. One set of use cases comes from the various ways
RFC 2445 allows date/date-time values to be represented in icalendar
It may be expressed in UTC or Zulu time. For example within an event
might have its start time specified by:
It may be expressed with a specific local time zone e.g.
It may be expressed with a floating time zone
In this last case the actual time is determined by having the time
zone supplied by the user or the user’s calendar application,
presumably that will be the user’s local time zone.
Uses for floating times might be to represent when the beginning of
the New Year is celebrated, which tends to happen at xxxx0101T000000
or midnight at the beginning of 1 January in each local time zone.
Or expressing that I wake up, or try to, at 7:00 a.m. in whatever time
zone I happen to find my body in.
The last RFC value for a time attribute is just a date e.g.
DTSTART:20090714 which is inherently floating with respect to time
That said, this discussion has been ignoring the fact that a time
might not represent a time of day, but can in certain cases represent
a duration, and there are differing standards on representing these.
RFC2445 has a period value which represents a signed time duration,
which can have week, day, hour, minute and second parts.
The Duration class in ActiveSupport is similar, it represents a signed
period with the same parts as are defined for Time#advance, years,
months, days, hours, minutes, and seconds. But as far as I can tell,
this really isn’t surfaced very well, in rails durations are pretty
much used as temporary results in time calculations.
And some SQL implementations, MySQL for one, have time values which
are really durations with hour, minute, and second parts. MySql allows
such a time to represent periods longer than a day, so 132:20:00 is a
valid time, although it would be a lousy time of day, except perhaps
for Bill Murray’s character in Ground Hog Day to use.