Getting offset for each time zones
Hi All, I wanted to get UTC offset for each time zone which is present under zoneinfo folder. basically I wanted to create a drop down for all timezones with UTC offset, where user can select timezone. Please let me know if it is possible to get UTC offset for all time zones in tz database. Thanks, KAILASH KUMAR JAIN Legal Warning: This message may contain privileged and confidential information. If you are not the intended recipient or for any reason think that this message may have been address to you or reached you as a mistake, its requested that you must not disseminate,copy or take any action in reliance on it and I ask you to delete all copies from your mail box and computer system and also notify me immediately by return e-mail.
I wanted to get UTC offset for each time zone which is present under zoneinfo folder.
In general, you cannot get a single offset for most time zones, as each time zone represents a series of one or more offsets and the transitions between them. For example, America/Los_Angeles uses UTC-8 during standard time, and uses UTC-7 during daylight saving time. You could get the *current* offset for each zone, but your list will vary depending on when you generate it. You could get the *standard* offset for each zone, but even the standard offsets have changed over time, so they would only be the *current standard* offsets. Additionally consider that in some zones the daylight time is a larger portion of the year than the standard time, and in general the list would not be representative of any set of offsets that were actually in effect all at the same point in time.
basically I wanted to create a drop down for all timezones with UTC offset, where user can select timezone.
The TZ project maintains lists in the zone.tab and zone1970.tab files that can assist in one particular way of selecting a time zone. You can consider building your list using these files. However, recognize that currently the comments in the file are only presented in English. If you are targeting a worldwide audience, then you have to pull in resources from the Unicode CLDR project to assist. If you were looking for specific code to implement, that depends highly on your particular platform and language, and would be better asked on a site like Stack Overflow than here. I'll also add that time zone selection is indeed a challenging problem, and there are alternative approaches to consider. These include map-based time zone pickers, lat/lon lookup via shapefiles, type-ahead style selection of associated cities (which requires even more data), multiple dropdowns used in succession, and others. Since most implementations don't make this easy, it's common to see a single dropdown with a long list of all TZ identifiers - even though that's not the recommended. You may want to spend some time looking at how various platforms differ in how they ask users to pick a time zone (mac vs linux vs windows), as well as web sites and applications such as Google Calendar. You may even want to try doing it in some language other than English to see what kind of differences there are. You'll find quite a lot of variation indeed. In general, I don't think the world has settled on a single right way for a user to pick a time zone. Regards, Matt
On May 18, 2016, at 8:58 AM, Matt Johnson <mj1856@hotmail.com> wrote:
I'll also add that time zone selection is indeed a challenging problem, and there are alternative approaches to consider. These include map-based time zone pickers, lat/lon lookup via shapefiles, type-ahead style selection of associated cities (which requires even more data), multiple dropdowns used in succession, and others. Since most implementations don't make this easy, it's common to see a single dropdown with a long list of all TZ identifiers - even though that's not the recommended. You may want to spend some time looking at how various platforms differ in how they ask users to pick a time zone (mac vs linux vs windows), as well as web sites and applications such as Google Calendar. You may even want to try doing it in some language other than English to see what kind of differences there are. You'll find quite a lot of variation indeed.
In general, I don't think the world has settled on a single right way for a user to pick a time zone.
...but Apple have done the best job I've seen so far for general-purpose OSes. ("General-purpose OSes" meaning "some small embedded device probably can't do as much fancy UI stuff".) The OS X time zone selector combines: lat/lon lookup via shapefiles for the "Set time zone automatically using current location" feature; a map-based time zone picker (presumably using the same shapefiles); type-ahead style selection of associated cities. iOS has the first and third of those (although it just calls the auto-select feature "Set Automatically"). I don't have Windows 10 handy to try it. Linux (and other OSes using free-software desktops) doesn't have a single desktop environment and thus doesn't have a single time zone selector, but I don't remember seeing anything as good as OS X has on either KDE or GNOME, although it might have gotten better since I last checked. I don't know what Android has, but I suspect, given that it's mostly used on small mobile devices, it supports "set automatically".
On May 18, 2016, at 12:31 PM, Guy Harris <guy@alum.mit.edu> wrote:
...but Apple have done the best job I've seen so far for general-purpose OSes. ("General-purpose OSes" meaning "some small embedded device probably can't do as much fancy UI stuff".)
The OS X time zone selector combines:
...
iOS has the first and third of those (although it just calls the auto-select feature "Set Automatically").
...and, unless I've missed something, *no* tzids *anywhere* in the time zone selector UI, so nobody's going to be complaining that the big city they're living in isn't the city mentioned in the tzid.
On Wed, May 18, 2016 at 11:58 AM, Matt Johnson <mj1856@hotmail.com> wrote:
I'll also add that time zone selection is indeed a challenging problem, and there are alternative approaches to consider. These include map-based time zone pickers, lat/lon lookup via shapefiles, type-ahead style selection of associated cities (which requires even more data), multiple dropdowns used in succession, and others.
An easy first question, particularly when selecting the local timezone, is "what (civil) time is it?" That narrows down the candidates considerably.
participants (4)
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Bradley White -
Guy Harris -
kailash kumar -
Matt Johnson