Talk:OpenHistoricalMap/Dates And Times

Discuss OHM, Dates and Time formats here

Vague dates

The new ISO for dates allows for vague dates.(the more vague ones so not 2000 but instead 19th century) Would those count as being unambiguous ? How should they be handled by the code ? --Ferdinand0101 (talk) 19:18, 23 December 2020 (UTC)

I've not yet seen the updated ISO document (they charge money for it) so I can't speak to its specific properties, but I expect it will be properly designed for machine parsing. I included the term unambiguous specifically because the OHM rendering engine will be parsing what is in the start_date and end_date tags. Maybe we can arrange for access to the document once OHM is brought into the OSM US Charter Project program. I would certainly prefer that we base whatever we do on prior, well considered art where such exists, and an ISO standard would certainly qualify Nfgusedautoparts (talk) 21:38, 23 December 2020 (UTC)

Basically the new standard allows me to just write '2000' and be done with it

And then it says that date is somewhere in the year 2000 so so far that's easy and works also for 2000-06 for saying June 2000 but for larger periods that really isn't possible (as far as I know)

(Source: the Wikipedia page for the new standard)

--Ferdinand0101 (talk) 07:48, 24 December 2020 (UTC)

Ian Dees brought EDTF to my attention and i've added it to the references. It's rather attractive as it has substantial provision for uncertainty, is designed to be ISO date format friendly, and is a standard from the LoC. Nfgusedautoparts (talk) 15:58, 24 December 2020 (UTC)

Given the needs for date specification even with uncertain dates, I think the EDTF/ISO interval format works really well. if start_date=1798/1802 that would indicate a start year somewhere in that range. we could use note or description tags to provide details and/or put details on the OHM wiki page devoted to the particular OHM project. either side of the / can be as vague or specific as needed using the provisions in EDTF/ISO.

Time Zones

Currently we're not doing much of anything about times. However, there may be projects that can make use of time specifications. How do we approach GMT/UTC vs local times? Modern time zones did not exist before 1878. Nfgusedautoparts (talk) 04:01, 24 December 2020 (UTC)

ISO 8601 permits arbitrary time offsets, and a time without a timezone designation means "local time". For pre-timezone times, you can figure out what offset would have been used, or simply leave it blank to indicate "local solar time" and let the computer figure out what offset that would be. --Carnildo (talk) 04:58, 24 December 2020 (UTC)

In the US pre 1883, times were generally referenced to solar noon in the nearest town. In my proposed plan to bring the Cope data from the Antietam maps in, I have times throughout the day that would be referenced to the nearby town of Sharpsburg MD. I'll have to think about this a bit. Nfgusedautoparts (talk) 20:45, 25 December 2020 (UTC)

The times are not precise enough to get overly fussy about this detail, but the relative relationship should be preserved, and any presentation should use the values that Cope entered on the map.

Vietnamese Calendar link: Spam or Reference Material?

The link to a "Vietnamese Calendar" that has been added to the "Reference Materials" section today does appear to be a site showing a calendar that is in Vietnamese language but otherwise not much different from the Gregorian calendar used in many other parts of the world. To me it does look a lot more like spam than reference material. I would be good if someone that speaks Vietnamese could have a look what it is. --Lyx (talk) 12:16, 28 March 2021 (UTC)

@Lyx: The site seems to be about the traditional Vietnamese calendar, showing both the traditional day names and Western-influenced month/day numbering (which doesn't necessarily align with the Gregorian calendar). But I don't see how any of these links are relevant to dates and times in OHM, other than to point out that we don't have support for non-Gregorian dates yet. – Minh Nguyễn ^💬 21:19, 30 April 2024 (UTC)