@shirayuki, this edit is unnecessary, inappropriate and unhelpful. In general this template should be deleted and we just use ISO dates, but if we have to pick a non-standard let's at least use one the majority of our users prefer?
Topic on Template talk:Date
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@Jdforrester (WMF), for example Extension:WikiEditor/en-gb is for British English and Extension:WikiEditor is for American English since Extension:WikiEditor/en-us doesn't exist.
But we should use ISO8601 dates.
No, en
is for all forms of English, and we choose wording carefully to work for as many people as possible; there are hundreds of variants of English, and if we were going to pick the most-spoken form that'd be en-in
, not en-us
. :-). If you want to create en-us
for I'll be in favo[u]r, but en
is not American English.