Lester Caine <lester@lsces.co.uk> wrote:
On 28/10/15 23:37, John Hawkinson wrote:
The time and the zone must be stored, becuse whther the time shifts with DST is a function of the zone. As long as the calendar app stores some things like "9:00am US/Eastern" (for a dentist appointment) and "13:00 UTC" (for an international conference call), calendar apps should work well.
SIMPLE things like that are not the problem. Where the problem arises is when the 9:00AM UTC Meeting in one location is advertised in several time zones and one of those time zones has a change of offset. The medical conference I quoted was across four time zones in Europe and the middle east, but one of the satellite links started an hour before the delegates arrived because of the change in DST at short notice. Don't ask why nobody even thought about the problem ... the local programs had been printed only with local times and the local organisers simply did not think ... current calendars do not do multi timezone well?
Yes. There is a problem with the way iCalendar is often used: calendar apps do early binding to timezone rules - not just the tz names, but embedding the actual schedule of DST changes in the calendar appointment object. This is a massive pain if the rules change. The best way to avoid problems is to bind to a time zone as late as possible. Sadly iCalendar doesn't allow the binding to be late enough. http://fanf.livejournal.com/104586.html Tony. -- f.anthony.n.finch <dot@dotat.at> http://dotat.at/ Fair Isle, Faeroes, Southeast Iceland: Southeasterly, veering southwesterly for a time, 5 to 7, occasionally gale 8 at first. Rough or very rough, occasionally high later. Rain or showers. Good, occasionally poor.