Talk:Time zone

Two different notions of "time zone" in the article

The article states that

A time zone is an area which observes a uniform standard time for legal, commercial and social purposes. Time zones tend to follow the boundaries between countries and their subdivisions instead of strictly following longitude, because it is convenient for areas in frequent communication to keep the same time.

Time zones are defined as one or two offsets from Coordinated Universal Time (UTC), and (if two offsets are used) the days when the offset changes. Some time zones switch between offsets throughout the year due to daylight saving time (DST).

This seems to correspond to the notion of time zones as possibly being per-polity, so that, for example, the US states of Arizona and New Mexico are not in the same time zone, as (most of) Arizona does not observe DST, but New Mexico does.

However, the map at the top of the article, which is captioned "Time zones of the world", shows time zones defined only by the standard-time offset from UTC, so that Arizona and New Mexico are in the same time zone, the North American Mountain Time Zone.

The notion of time zone used in the tz database is closer to the first one, although that notion has to handle more than just standard and daylight saving time. For example:

• the rule that specifies when the offset changes can themselves change over time, and have changed in a lot of places, although, if "the days when the offset changes" refers to a set of rules for determining, for any given year, the days when the offset changes, that's handled by the definition above;
• Morocco adjusts its clocks for Ramadan;
• some entries in the tz database include the region the entry covers moving from one standard-time UTC offset from another.

See, for example, the map at the top of the tz database article, which is more complicated than the map at the top of time zone.

Some tz database documentation uses the term "timezone", with no space between "time" and "zone", to refer to the regions that a tz database entry covers, in a somewhat-subtle attempt to distinguish tz database entries from "time zones" in the sense in which "time zone" is used in the caption for the map. Guy Harris (talk) 22:24, 8 March 2024 (UTC)

@Guy Harris: I propose replacing the map with this SVG version that I recently made. It uses stripes for areas that observe two offsets, so it's closer to the definition in the article. In addition, this version uses intermediate colors instead of stripes for fractional hour offsets, which I think is clearer; lists the dates of offset changes below the map; uses less memory than the PNG version, without losing resolution; and can be edited more properly.

I think that the definition in the article already includes the case of Morocco. For clarity, I suggest changing the last sentence to: Some time zones switch between offsets throughout the year, usually due to daylight saving time (DST).

The tz database groups areas in the same time zone only if they have always shared the same time since 1970. But the map only considers what they currently observe. Heitordp (talk) 13:58, 10 March 2024 (UTC)

The proposed map applies to the "a zone represents a standard time offset from UTC" definition of "time zone", with stripes to indicate the portions of the zone where DST is observed"; it doesn't show differences between either current or past rules.

The article says

Time zones are defined as one or two offsets from Coordinated Universal Time (UTC), and (if two offsets are used) the days when the offset changes. Some time zones switch between offsets throughout the year due to daylight saving time (DST).

which covers Morocco in that it has two offsets; the second sentence doesn't say that the two offsets are necessarily due to DST, so that also can include the two offsets being due to Ramadan. Guy Harris (talk) 23:26, 10 March 2024 (UTC)

@Guy Harris: The map that I proposed does show the differences between current rules, as it lists the dates of offset changes for each area below the map. It doesn't show past rules, but I think that it would be impractical to do so. Heitordp (talk) 07:33, 17 March 2024 (UTC)

Morocco and Spain appear to be in the same "time zone" according to the map on time zone, but they aren't in the same tzdb timezone ("timezone", without a space between "time" and "zone"), as mainland Spain (Europe/Madrid) is currently following the EU DST rules, but Morocco (Africa/Casablanca) is currently following Morocco's Ramadan rules.

It's probably best not to even try to come up with a map for IANA time zone database timezones - if somebody wants that they should go to tz database and look at the map on that page - and decide what this page is to discuss, namely "offsets from UTC, "time zones" as most people think of them, or "timezones" (the term the tzdb documentation uses) or "tzdb regions" (the term I've used one occasions) meaning "everything that has its own tzdb ID". Guy Harris (talk) 08:20, 17 March 2024 (UTC)

Time zones are definitely regions, not offsets, as explained in the blog post cited in the article. But the exact regions that constitute the various time zones are not necessarily the ones in the tz database. It depends on which period is considered. The tz database considers all offsets used in each location since 1970, resulting in about 300 time zones (not counting aliases), most of which consist of smaller zones that only differed from larger ones many years ago. But that period is arbitrary. If we consider 1850, when each city used a different offset, there may be thousands of time zones. Conversely, if we consider 2024, there are only about 64 time zones, which are shown in the second map and table in the article. I think that the latter is what people mean when they speak of time zones. They still mean regions, but the ones that currently share the same time, possibly including currently scheduled changes such as DST but disregarding historical differences.

For this article, I suggest a simpler text that should fit any notion:

All time zones use offsets from Coordinated Universal Time (UTC). The offsets range from UTC−12:00 to UTC+14:00, and are usually a whole number of hours, but a few zones use offsets with an additional 30 or 45 minutes, such as in India and Nepal. Some areas use a different offset for part of the year, typically one hour ahead during spring and summer, a practice known as daylight saving time.

If the map is going to show each area with only one offset, I think that it makes more sense to show Morocco in UTC+1 because that's what it uses for almost the whole year, except one month. But I propose this map, which uses stripes for areas that use two offsets. Morocco is shown with stripes of UTC+1 and 0, and Spain with UTC+1 and +2, and below the map it lists the period when each place uses the second offset. I don't find the map of the tz database very useful, because it only shows the boundaries of time zones, but not what offsets they use. Heitordp (talk) 22:52, 19 March 2024 (UTC)

Time zones are definitely regions, not offsets, as explained in the blog post cited in the article. The US Standard Time Act of 1918 doesn't use the term "time zone", but does speak of "the territory of continental United States" being "divided into five zones", with each zone being given specific "standard time"s, and specifying that each zone's time gets "advanced one hour" "at two o'clock antemeridian of the last Sunday. in March of each year" and "by the retarding of one hour, [returned] to the mean astronomical time of the degree of longitude governing said zone" "at two o'clock antemeridian of the last Sunday in October in each year". So those zones have both geographical boundaries "defined by an order of the Interstate Commerce Commission" and standard time offsets. The DST part of the Standard Time Act was repealed in 1919; the term used was, again, just "zone". In practice, some places adjusted the clocks twice a year and some didn't; it was not zone-dependent - one place within a zone might observe DST and another place might not, so, while a given zone has a specific standard time offset, the rules for adjusting the offset may differ between places in the zone.

The Uniform Time Act of 1966 re-standardized DST, as well as adding more zones; the terminology remained "zone". It allowed states to opt out of DST - Arizona did so - but did not give states that did so separate zones, so a "zone", in US law, has geographical boundaries and a single standard time offset from UTC, but does not have a single set of time-change rules, so a "zone" does not correspond to a tzdb "timezone"/region. In particular, both Arizona. which does not observe DST, and New Mexico, which does, are in the same "zone" which, to use the terminology of the Standard Time Act of 1918, has, as its "standard time", a time that is "known and designated as United States Standard Mountain Time". That zone is generally called the Mountain Time Zone, although it appears that the name "Mountain Time Zone" - and the other such names - aren't specified, as such, in US law.

As far as I know, when people speak of "time zones" in the US, they're speaking of the zones as established by the aforementioned acts, meaning that, for example, both Arizona and New Mexico are in the "Mountain Time Zone", not in separate zones.

Canada appears to have set up standard time with the Reckoning of Time Act in 1890, which specified the standard times of specified provinces and territories, rather than specifying "zones" in the US sense.

In that blog post, Denver Hamilton might be arguing that people talking about times on computers use the term "time zone" to refer to tzdb timezones/regions, rather than to "zones" in the US sense, but he also acknowledges that "zones" in the US sense "are also called “time zones” in casual conversation". I don't think Wikipedia will be all that successful to get people to talk about, for example, the America/New_York time zone rather than the Eastern time zone, so the time zone page will have to deal with the common use of "time zone".

I think that the latter is what people mean when they speak of time zones. They still mean regions, but the ones that currently share the same time, possibly including currently scheduled changes such as DST but disregarding historical differences. Again, as far as I know, people think of both Arizona and New Mexico as being in the Mountain Time Zone even though their clocks don't always agree - it's more like "Arizona and New Mexico are in the Mountain Time zone, but Arizona doesn't do DST while New Mexico does", so it's more like "currently share the same standard time offset". That wouldn't correspond to the tzdb even if the tzdb combined all locations with the same offset and rules since 2024-01-01, as that tzdb would have Arizona and New Mexico in separate tzdb regions/timezones.

And, on top of that, a tzdb region/timezone doesn't necessarily have a single standard time offset - the standard time offset of a location may change for various reasons, including "state/province/etc. X moved to a different standard time offset" (which has happened) and "country X seized that location from country Y, or that location left country Y and joined country X or became a new country Z, and the standard time offset was changed", and so on. The blog post in question mentions Coral Harbour; see {{section linkTime in Nunavut#History]] for what happened (which does not appear to be in the tzdb - I'll mention that on the tz mailing list) - that's one case of "moved to a different standard time offset".

The online Merriam-Webster Dictionary says that "time zone" means "a geographic region within which the same standard time is used". A Google search for "definition" "time zone" shows a definition from "Oxford Languages" stating that a time zone is "a range of longitudes where a common standard time is used". This, again, suggests that the common meaning of "time zone" has nothing to do with time adjustments, it's just "a region with a given standard time offset".

So tzdb regions/timezones will probably forever remain different, at least for some locales, from what many people think of as a "time zone".

So I'd use

A time zone is an area which observes a uniform standard time for legal, commercial and social purposes. Time zones tend to follow the boundaries between countries and their subdivisions instead of strictly following longitude, because it is convenient for areas in frequent communication to keep the same time.

Time zones are defined by the standard time offset from Coordinated Universal Time (UTC). Some locations within a time zone may adjust the clock during the year. For example, locations may switch between offsets throughout the year due to daylight saving time (DST). The UTC offsets range from UTC−12:00 to UTC+14:00, and are usually a whole number of hours, but a few zones are offset by an additional 30 or 45 minutes (such as in India, South Australia and Nepal).

as the beginning of the article, dropping the notion that DST rules are part of a time zone.

I don't find the map of the tz database very useful, because it only shows the boundaries of time zones, but not what offsets they use. It's more than just offsets, it's offsets and when various offsets were, or will be, in effect. I suspect a map that shows all that information would be complicated enough to make readers' eyes bleed. Guy Harris (talk) 03:59, 20 March 2024 (UTC)

I agree with everything that you wrote. Feel free to change the text in the article as you proposed.

What do you think about changing the map to this version that uses stripes for areas with DST? I think that it still matches the text that you proposed, as it shows the boundaries between time zones based on standard time, but it's more accurate for the purpose of showing the offset used in a location. Heitordp (talk) 10:42, 24 March 2024 (UTC)

It appears that Morocco is striped, so it doesn't only use stripes for areas with DST, it uses stripes for areas that adjust their time away from standard time during the year, whether or not that's DST, which is the right thing to do. I.e. not all adjustments away from standard time are for DST.

So that map would be appropriate. Guy Harris (talk) 17:26, 24 March 2024 (UTC)

References

Semi-protected edit request on 5 April 2024

2601:447:CA83:8760:F928:602D:BFBE:BC32 (talk) 22:39, 5 April 2024 (UTC)

No request made so request denied. Jc3s5h (talk) 22:46, 5 April 2024 (UTC)

Madras Time

copied from your own page on Madras Time to be added to the history section. Other countries are mentioned and this was the first in 1802 2A02:C7C:3765:1C00:F3B9:BC52:375F:1AB7 (talk) 11:20, 12 May 2024 (UTC)

Incorrect map

Part of Ukraine marked as Russian territory! 5.173.146.26 (talk) 10:44, 5 July 2024 (UTC)

It's not marked as Russian territory. The international borders on the map are white lines, and the border between Ukraine and Russia is shown as internationally recognized. The red lines are only the separation between time zones. The red line separating the occupied part of Ukraine from the rest of the country is just like in other countries with more than one time zone. Heitordp (talk) 12:41, 5 July 2024 (UTC)

Ukraine did not make decisions about changing time zones in the Temporarily Occupied Territories.

Therefore, within the internationally recognized borders of Ukraine, a single time zone applies throughout its territory. FarCryMan (talk) 13:54, 22 July 2024 (UTC)

@FarCryMan: The map is supposed to show the time zone that is actually used in each location, regardless of laws or how it was decided. The occupied territories of Ukraine actually use UTC+3, so the map shows them this way. There are also other areas in the world that use time zones different from what is defined by law (for example in Australia, Canada and United States), and the map shows their actual practice. Heitordp (talk) 14:39, 22 July 2024 (UTC)

Where do you get information about the actual timezone used in these territories?

Please provide the source. FarCryMan (talk) 19:59, 22 July 2024 (UTC)

@FarCryMan: Several news articles reported that Crimea and the portions of Donetsk and Luhansk regions administered by separatists or by Russia changed to Moscow time in 2014:[1][2][3] Similarly, several news articles reported that the parts of Ukraine occupied by Russia in 2022 also changed to Moscow time: "our city lives by Moscow time",[4] "Mariupol is now in the Moscow time zone",[5] "Currently, Moscow time is de facto in effect in the new regions",[6] "the regions had shifted to Moscow time".[7] Heitordp (talk) 21:39, 22 July 2024 (UTC)

@Heitordp Sorry, but you're wrong. The map is supposed to show the time zone that is actually used in each location, regardless of laws or how it was decided - time zone itself is an artificial concept created by humans, that doesn't actually exist "regardless of laws". Each person technically can live by any time zone he wants. The occupied territories of Ukraine actually use UTC+3 - who exactly uses it? Government appointed by russians or people living here? Are you 100% sure that the population of occupied territories actually live by Moscow time and not the Kyiv one?

Russians can claim anything, but there is such thing as international law. This is why, for instance, official political maps of the world and Europe don't present occupied Ukrainian territories as part of the RF. AFAICS you're the only editor (and creator) of both maps, but, in my opinion, such disputed changes shouldn't be done based on the opinion of only one person. I suggest reverting edits related to Ukrainian time zones until a consensus between multiple users is reached. Thanks! Прусак (talk) 00:56, 19 October 2024 (UTC)

@Прусак: The time zone of an area is whatever time the people in that area use for practical purposes. Usually it matches the law, but not always. As I mentioned above, there are many areas in the world that use a time that is different from what the law defines. For example, these maps from the Canadian government show the areas with the time that is legislated and what is actually observed; they are different in most of Labrador and in parts of Ontario, Saskatechewan and British Columbia. These articles explain the situation in Labrador:[8][9] Similarly, several small areas in the United States use a time that is different from law:[10] A small portion of Western Australia also uses a time that is not defined by law:[11][12]

It's not that "Each person technically can live by any time zone". In the examples above, everyone in the area agrees that this is the time used there, and it's even displayed on road signs and public clocks, even though it's not according to the law. All of these "de facto" times are also implemented in the IANA time zone database, which is used by most computer systems worldwide, and in the time zone maps in Wikipedia.

The news articles that I cited in my previous reply say that the Russian government has implemented many Russian standards in the occupied regions of Ukraine, not just Moscow time but also public signs, currency, schools, telephone and television networks. I can't be totally sure if the whole population there really uses Moscow time, but that's what the news articles suggest. I know that most people there oppose the Russian occupation, but it would be impractical for them to privately use a different time from that the public services, transportation and telecommunication systems use in their area. At least in Crimea, which was annexed by Russia in 2014, it's very clear that the people there use Moscow time, as shown in these articles:[13][14] The IANA time zone database also includes Crimea in Moscow time.

I created the two SVG maps currently in the article here, but previously there was a PNG map, which another user had created. This PNG map already showed Crimea and a portion of Donetsk and Luhansk regions in UTC+3 since 2015. In 2023, a user commented that the other recently occupied areas of Ukraine should also be shown in UTC+3, so I edited the map to include them at that time. You can see that discussion here. It wasn't just my opinion. Later this topic was also discussed multiple times by other users, and the consensus each time was to keep the map as it is, showing the "de facto" time zones. Please see the discussions here, here and here. Later, I just replaced the PNG map with the SVG version, but I kept how Ukraine was already shown.

However, I understand that many users still disagree with how Ukraine is shown, so I'll start another discussion below. Heitordp (talk) 00:30, 20 October 2024 (UTC)

Thanks for clarification and pointing out to previous discussions. I can see your point here, but can't totally agree with it. Anyway, appreciate your willingnes for discussion Прусак (talk) 13:14, 20 October 2024 (UTC)

Wikipedia is now run by wannabe dictators who don't like democracy, it's pointless to try to reason with them. The whole of Ukraine, including all temporarily occupied parts of it, is in one time zone. No idiot can change that. 109.87.36.102 (talk) 21:20, 2 September 2024 (UTC)

Wikipedia is based on reliable sources. If you provide a reliable source that says that the occupied territories of Ukraine actually use UTC+2 in practice, I can change them on the map. I don't support the invasion of Ukraine either. Heitordp (talk) 22:14, 2 September 2024 (UTC)

RFC on Time zones of Ukraine and Georgia

The maps of time zones in Wikipedia (SVG, PNG) show the time actually observed in each area, de facto, regardless of legality. For example, the maps show certain parts of Australia, Canada and the United States in the time that they actually observe even though it's different from what the law specifies there. Similarly, the maps show the occupied regions of Ukraine and the separatist regions of Georgia in UTC+3, which is the time enforced by the Russian or separatist authorities there. Previous discussions about this topic resulted in keeping the map de facto, including the occupied or separatist regions in UTC+3, but many users continue to complain about it, so I'm restarting the discussion here. How should the maps show the time zones of the occupied regions of Ukraine and separatist regions of Georgia? You may answer differently for each region.

Please note that the maps still show these regions as part of Ukraine and Georgia, with the international borders as generally recognized. The question here is only regarding the time zones. For reference, the IANA time zone database includes Crimea in UTC+3, but it doesn't mention the other occupied regions of Ukraine or the separatist regions of Georgia. Heitordp (talk) 02:06, 20 October 2024 (UTC)

• Keep all in UTC+3, which is de facto. Heitordp (talk) 02:08, 20 October 2024 (UTC)
• Keep all in UTC+3 It makes sense. We tend towards 'de facto' in other areas. No reason for not mentioning the 'legal' situation though.Lukewarmbeer (talk) 08:55, 20 October 2024 (UTC)
• Keep all in UTC+3 defacto information is useful, when someone wants to communicate with people in the area. ChristianKl ❪✉❫ 11:28, 20 October 2024 (UTC)
• Use the legal time, since it is more reliably verifiable. Using what we think the de facto time is or "should" be sounds like original research, and at very least is a neutrality problem, of WP siding with occupying military or separatist militia forces in various places, without any regard to whether the everyday civilian population in these places is actually going along the perhaps temporary regime's time preferences. (Prefering the legal time zone, however, satisfies WP:DUE, since it will better agree with more of the available sources.) I'm not at all swayed by the "useful, when someone wants to communicate with people in the area" idea, since the difference is only an hour, and if you need to have a voice call or e-conference with someone in such a place you can ask them when to call, with regard to what time zone, in the course of setting that up and agreeing to do it.  — SMcCandlish ☏ ¢ 😼  14:19, 20 October 2024 (UTC)

  In my opinion, this doesn't really solve the problem, because you still have to make a judgement about whose law you report. Both Ukraine and Russia claim the right to pass laws in Donetsk; right now, the laws passed by Russia are more likely to actually be enforced, but the laws passed by Ukraine are considered by many other countries to have more "moral right". In order to be neutral, you would need to adhere to some very strict definition, like "the time zone according to the law as passed or recognised by the country which the majority of UN member states consider to have rightful sovereignty of the territory". That might mean we need to research what hypothetical time zone "should" be in effect on the island of Taiwan according to the People's Republic of China, in the interest of "fairness", but against all common sense. - IMSoP (talk) 21:52, 23 October 2024 (UTC)

  Many reliable sources have reported that these regions use UTC+3:[15][16][17][18][19][20] so this is not original research. The IANA time zone database also includes Crimea in UTC+3.[21] Meanwhile, I haven't seen any source saying that the civilian population in these regions is using another time, which I also find unlikely as it's impractical for people to use a time different from public services. Some of these regions have used UTC+3 since 2014 so at least there it's not temporary. In addition, "legal time" is unclear because Russia and separatists have also passed laws to specify UTC+3 in these regions. In my opinion, the best way to satisfy neutrality is to rely on the time actually used, not on the law of either side. Heitordp (talk) 15:06, 27 October 2024 (UTC)

• Possible compromise: highlight the disputed areas. The map currently uses hatching to indicate areas which change their clocks every year; perhaps some other style could be used to indicate a region where, for one reason or another, the situation is not straightforward. Each such area could be marked with a letter referring to a footnote, where we could explain the details. That way we could find references for what "de facto" usage exists, and explain interesting cases such as Labrador mentioned above, which definitely seems like a fact worthy of an encyclopedia. - IMSoP (talk) 19:07, 24 October 2024 (UTC)

  I think that highlighting the areas and adding a footnote would add unnecessary emphasis to the dispute. Instead, as a compromise I suggest keeping the disputed areas shown with the current colors, but moving the brown line separating time zones to match the internationally recognized border between Ukraine and Russia. This way the occupied regions of Ukraine would look similar to the rest of the country, just blue rather than hatched red and blue, but with no line between them.

  I suggest making this change only for Ukraine, and perhaps for Georgia, but not for the parts of Canada, US and Australia as no one has complained about them. The difference between legal and actual time in these areas is indeed worth mentioning in their respective articles on Wikipedia, and it already is, but I think that it would be excessive to also represent it on the map. Heitordp (talk) 15:42, 27 October 2024 (UTC)

• It can be misleading if borders are drawn with respect to international recognition but time zones are demarcated according to de facto occupation. Senorangel (talk) 03:44, 25 October 2024 (UTC)
• Accept that we cannot be authoritative in contested areas. That doesn't mean we throw in the towel, but rather we need to choose an authoritative source (such as IANA) just like we're choosing some sort of specific source for the country boarders, and simply disclose that on the document itself. Otherwise the option is to somehow indicate, as IMSoP mentioned, that the area is contested or otherwise does not follow IANA. We don't necessarily need to draw significant attention, but rather replace the UTC offset by either an astrisk or other symbol of the same size and weight that is called out as a footnote on the document. People should not be surprised when they see that indicated on the map. TiggerJay (talk) 06:41, 8 November 2024 (UTC)

  The IANA tz database makes an attempt to be as "authoritative" as possible with respect to the UTC offset and DST rules for the time that's commonly used. Europe/Simferopol is the tzid for Crimea, and reflects the switch to Moscow time. However, when it comes to the Donetsk Oblast and Luhansk Oblast/Donetsk People's Republic and Luhansk People's Republic, as per a message from Paul Eggert, the main tz database maintainer, those were deemed to "[fall] under the "war or insurrection" clause of the timezone identifiers guideline <https://data.iana.org/time-zones/theory.html#naming>", so no new timezone (in the tz database sense) was created; "As a practical matter, belligerents can use TZ='Europe/Moscow', TZ='Europe/Kyiv', or TZ='Asia/Tbilisi'...", so it's "authoritative" answer is pretty much "we're sticking with Ukranian and Georgian time for now, but you can choose to use Moscow time if that's what works for you". Guy Harris (talk) 08:02, 8 November 2024 (UTC)

That's a good find, but I would interpret its conclusion slightly more subtly. The tz database does not define the geographic boundaries of zones, but it does record their history; recognising a border change requires creating at least one new zone, choosing a name, and documenting when civil time changed in that named region. Eggert's comment is deferring to a later date the decision on how many new zones are needed, if any, and when their change in UTC offset should be documented as occurring. It leaves it up to the user how to handle things in the meantime, choosing either Europe/Kyiv or Europe/Moscow.

The tz database documentation contains links to related projects, including timezone-boundary-builder, which combines the tz database with OpenStreetMap data. Notably, that project has a file of "expected overlaps" which currently includes Abkhazia as overlapping between Asia/Tbilisi and Europe/Moscow.

I don't know much about the OpenStreetMap project, and where this issue would have been discussed, but marking Abkhazia as disputed is presumably a position they have been willing to adopt, if I'm understanding that "overlap" file correctly. Being another community-sourced project, I'm not sure we could defer to them as "authoritative", but they may have adopted a specific policy which would be relevant to this debate. - IMSoP (talk) 18:11, 10 November 2024 (UTC)