[duijf]

More likely May 2021, the date format at the bottom of the post is probably YYYY-MM-DD as common in Germany where the author seems to be located.

EDIT: If Germany has the same conventions as The Netherlands, DD-MM-YYYY is probably even more common

[capableweb]

There is a meta tag in the article source code that removes all ambiguity (since 99% of the time it is specified in ISO 8601):

    <meta property="article:published_time" content="2021-05-10T22:00:00+02:00">

[Semaphor]

YYYY-MM-DD is the standard in Germany, most people don’t know that and essentially no one (including in official documents) uses it. Never seen it anywhere outside computer nerds who like sortable dates. So yeah, DD-MM-YYYY is the normal way here.

[llampx]

I would add that if DD comes first, the format is usually DD.MM.YYYY. Or DD/MM/YYYY, which is more common in the UK. Rarely have I seen dashes when not following the ISO 8601 YYYY-MM-DD standard.

[arrrg]

I was taught DD.MM.YYYY in school (90s). This is the de-facto standard (short) date format in Germany and by far the most commonly used one.

First because it’s consistent with the longer written out date format used in German: „19. Januar 2022“ (19th of January 2022) – note the dot after the 19.

Second because it’s also consistent with how it’s spoken. The dot denotes ordinal numbers in German and that’s also how the date is spoken: „Neunzehnter Erster Zweitausend Zweiundzwanzig“ or “nineteenth first two thousand twenty and two”.

Dashes and slashes are highly likely to be confusing to people if used in that context, though advisable if you are using any other date format because then at least people will be weirded out and likely pay closer attention if there’s anything going on with that date.

It is true that DIN 5008 (which defines rules for word processing and does have some weight in professional circles) recommends YYYY-MM-DD, however this way of writing the date never took hold in Germany (just because it’s part of a norm doesn’t make it commonly used or accepted) and DIN 5008 does actually allow for DD.MM.YYYY.

[arrrg]

YYYY-MM-DD is, as far as I know, merely a recommendation in DIN 5008, not in any way the standard in Germany, either officially or informally. DIN 5008 does allow for DD.MM.YYYY (with the dots and without spaces), Duden recommends spaces after the dots.

[Semaphor]

I looked it up again, you were more right than me ;) If you speak German, you can read about it on Wikipedia [0], essentially it was the only format from 1996 till 2001, but because it was completely ignored, they went back to allowing DD.MM.YYYY, since 2020 it also includes that the old format is only to be used for national mail.

[0]: https://de.wikipedia.org/wiki/Datumsformat#DIN_5008

[elzbardico]

A good heuristic is that if you are outside US, assume DD-MM-YYYY.

[sampo]

We don't need to assume, there is "2021-05-10" in the bottom of the article.

[SAI_Peregrinus]

To be pedantic that still requires assuming the author is using a sane convention (RFC3339) or convention including sane formats (ISO 8601) and not something ridiculous like %V-%W-%O or %Y-%D-%M. Thankfully the sane convention seems highly likely.