Re: syntax to specify time scales

More syntax reference. I've done a quick survey of interpretations of $TZ. I'll also throw in a couple of formats not used in $TZ. glibc tzset() interpretation of $TZ --- Accepts a subset of POSIX format. Does not document (but does support) the option to omit t

Re: syntax to specify time scales

Zefram schreef: > It also explicitly lists some that are based on GMT: the European Union, I don't think this is actually true. The page quotes a European directive on summer time. Directives of the European Union are published in all official languages of the EU, and all of the versions are equal

Re: syntax to specify time scales

Eugene van der Pijll wrote: > Lord Tanlaw refers to the UK as the only >industrialized country that has its legal time based on GMT. But there >are probably a lot of former colonies that have not changed their time >laws. Found a source for more on this.

Re: syntax to specify time scales

Zefram schreef: > My intention was that you'd be able to name a GAT+offset zone if useful. > The offset syntax is for occasions when an unnamed zone is temporarily > required. Perhaps Riyadh would be a GAT based time zone, and perhaps in Victorian times, there was a regulated system of time zones

Re: syntax to specify time scales

For reference, the POSIX definition of $TZ syntax is at . In summary, POSIX defines the meaning of $TZ strings matching $posix_tz below: $abbrev = qr#[A-Za-z]{3,}|\<[-+0-9A-Za-z]{3,}\>#; $offset = qr#[-+]?([01]?\d|2[0-4])(:[0-

Re: syntax to specify time scales

Eugene van der Pijll wrote: >OK, so a "legal Europe/London" timezone is meaningful (though not really >useful). As long as you're not proposing to change the Europe/London >timezone itself. I'd initially imagined actually changing Europe/London, but on reflection I realised that would be awfully d

Re: syntax to specify time scales

Zefram wrote: Rick Measham wrote: my $riyadh_lmt = DateTime::TimeZone::LMT->new( longitude => 46 + (43 / 60) + (27 / 3600) ); How much error in time conversions is introduced by the floating point rounding? DateTime allows for a one-second precision in the offset, so while LMT passes a f

Re: syntax to specify time scales

Zefram schreef: > So *legally speaking* the standard time in the UK is based on what we > now call UT1. It is an astronomical timescale. I've read some of the relevant parliamentary debates now, and you're right. That still doesn't mean that our TZ Europe/London should be based on UT1: the time t

Re: syntax to specify time scales

Eugene van der Pijll wrote: > it's the difference >between GPS and TAI(GPS) that is fixed, right? Forgot to reply to this earlier. Yes, strictly speaking the equation is TAI(GPS) = GPST + 19 s I've been using the term "GPS time" slight

Re: syntax to specify time scales

Rick Measham wrote: >my $riyadh_lmt = DateTime::TimeZone::LMT->new( >longitude => 46 + (43 / 60) + (27 / 3600) >); How much error in time conversions is introduced by the floating point rounding? >A thought: it might be good to somehow include the ability to load other >TZ modules from a str

Re: syntax to specify time scales

Eugene van der Pijll wrote: >> Civil time in the UK is not legally based on UTC; > >I believe this to be incorrect. British Standard Time, aka >"Europe/London", certainly observes leap seeconds, and is therefore >based on UTC. Maybe the legal definition is still in terms of GMT, (The name "British

Re: syntax to specify time scales

Eugene van der Pijll wrote: If I were to implement these time scales for DateTime, I would probably implement them as subclasses of UT1 (or "LMT") and LAT, with the geographical longitude as parameter; "LMT+46d43m27s" for Riyadh legal time, for example. But your notation is reasonable as well.

Re: syntax to specify time scales

Zefram schreef: > I note that DT::TZ::TAI > attempts to treat TAI as a timezone, which doesn't work 100% but does > put TAI in roughly the right relationship to the other DT objects. As you say, TZ::TAI does not work 100% prefectly. It has turned out to be impossible to implement it correctly, bec

syntax to specify time scales

I'm developing some code that provides a real-time clock display, in conventional hours-minutes-seconds format, and handles multiple time scales as well as ordinary UTC-based timezones. As a result, I need a way for users to textually specify which time scale to use. I'd like this syntax to be dis