It's good to know that such an option is planned for future releases. I presume, once implemented, this would mean that if a person selects, say, DD.MM.YYYY, Zotero will modify all entries, no matter how they were originally formatted (e.g., 5 May, 2020; May 5, 2020, 2020, May 5, etc, etc)?

I can understand that each detail view might show the date as it was entered even if it's stored as DD.MM.YYYY in the database.

But is there really no way to view a list of my entire library and see them all in the same date format? Otherwise, when I click on sort and there are DD.MM and MM.DD dates mixed together, it appears that they're actually not sorted. This drives me crazy because I have to go through the entire list and look at the detail view to verify that the date is entered correctly or not. And on those detail views, it's not sufficient to just have all be in the same date format. I need to read carefully to learn which date format was assigned to each item and then verify that it's correct. For the project that I'm working on now, I can still remember what's 4.8 or 8.4, but in a year from now I might not remember anymore what was correct.

It's also especially a concern for collaborative libraries. Someone with a system setting of MM.DD may read the library list and see that all dates appear to be in DD.MM. Then that person would create many additional entries all in DD.MM, even when their local system settings are in MM.DD. So this would then result in them entering the dates incorrectly. I've already caught this error several times from my colleagues.

This kind of user behavior makes sense because nearly all online forms require the user to enter dates in a particular format, not according to their own system settings. Also excel has a single date format per column and it's displayed consistently.

By when do you think this change will be implemented? From the forum posts, it seems like it's been discussed already for quite some time. I'd prefer an intuitive solution instead of needing to constantly remind our team to double-check their system date settings and to enter them in that way in Zotero.

For the project that I'm working on now, I can still remember what's 4.8 or 8.4, but in a year from now I might not remember anymore what was correct.

@rohrkemper: For now, for a group with people from multiple locales, it's better to just enter the dates in an unambiguous format — e.g., with the month name written out, or as YYYY-MM-DD.

I assume the "extra parts" would be references that have, for example, two years in the date field (e.g., 2018/2019) or ambiguous additional date information (e.g., a random number that isn't clearly a year, month, or day)?

@sciwonder: Yes, though Zotero will support additional date formats in the future for things like date ranges and ambiguous dates (in the historical sense, not the syntactical sense), so the number of cases where there are extra parts will decrease.

There's no way to identify items with extra date parts through the UI at the moment, but here's a script you can run in the Run JavaScript window:

var items = await Zotero.Items.getAll(Zotero.Libraries.userLibraryID, true);
var pairs = items.map(item => {
var date = item.getField('date', false, true);
if (!date) return false;
var parsed = Zotero.Date.strToDate(date);
if (!parsed.part) return false;
return [item.key, item.getDisplayTitle(), date];
})
.filter(x => x);
return pairs;

(This is for your personal library. Doing it in a group library would require a little adjustment.)

This might be a bit unrelated but I am looking for ways to toggle the display of dates in fields such as "Accessed". While I always enter dates as YYYY-MM-DD and while my OS (macOS) is set to YYYY-MM-DD, Zotero displays dates following the US custom of MM/DD/YYYY, which is highly confusing.

@dstillman Thank you very much for the quick reply. Changing the language in the Advanced pane of the Zotero preferences to "English (UK)" at least changes to DD/MM/YYYY. It would be great if one could get a plain old YYYY-MM-DD format with a future update.
Best,

@psyguy: It's right at the top of the Advanced → General pane in the preferences.

I would also like to have a consistent date format in the display (and export). Currently, when I export the metadata of an item to a markdown file (using zotero-mdnotes), the inconsistent format of the dates in the exported file makes it impossible to sort.

I'd like to have YYYY-MM-DD format as well, especially if for this case, Zotero already uses this format internally. Another place the less-ideally-formatted date pops up is when using the 'Add Note from Annotations' option after annotationing a PDF within Zotero, which produces a note with this title: "# Annotations (11/25/2022, 9:23:45 AM)". It would be great to have access to the format of the date (and 24-hour time, etc.) here for uniform searchability.

Both plugins [Jasminum](https://github.com/l0o0/jasminum) and [zotero-format-metadata](https://github.com/northword/zotero-format-metadata#readme) provide the function to convert Date to ISO YYYY-MM-DD format, hope it is useful for you.