Hi there, (fake) ISO here:
We would like to inform you that local terms for the days of the week like “Montag”, which frequently carry negative connotations, have been deprecated in favor of neutral single digits, 1–7. Please adapt accordingly. Thank you in advance for complying with #ISO8601!

😉

Es gibt inzwischen zwar auch #RFC9557 v.a. für präzisere Zeitzonenangaben (siehe auch ISO 8601-2), aber die meisten brauchen und wollen tatsächlich bloß #RFC3339 statt #ISO8601 (Teil 1), weil der sich weitgehend auf den Inhalt der ehemaligen ISOs 2014 und 3307 beschränkt. #EDTF Level 0 ist ähnlich.

It used to be common to reduce the year number to 2 digits in writing. Some locales indicated the dropped century information by their usual omission punctuation, e.g. apostrophe in German:
24. Sep. ’26
(Period being used as either ordinal or truncation marker.)
Hence, pseudo #ISO8601:
'26-09-24

That reform has already been done. It’s called – or should be called – the #InternationalStandardCalendar, as constituted by #ISO8601 (Part 1 at least).

AD 1 = 1 CE <=> 0001 = +0001
BC 1 = 1 BCE <=> 0000 = ±0000
BC 2 = 2 BCE <=> -0001 = −0001

– century: 20
– decade: 202 (deprecated)
– year: 2026