European here. When I state my date of birth I state it as “7th of October 1990”.

When a date is within the current year I state it as for example “27th of June”.

If weekday matters, and specific date is still relevant I’ll say for example “Monday 27th of June”.

I might also simply say “Sunday last week”, “Monday next week”, “Monday at the end of next month”, etc.

Likewise I might say “a couple of weeks ago”, “last week”, “a few days ago”, “in under two weeks”, etc.

Depends on context.

When including a date in a file name I prefer YYYY-MM-DD for date.

When using dates in a directory hierarchy I’ll have years on the top level, with months within them and dates within those.

Sometimes I might use a format like YYYY-mm-ddTHHMMz_s in a file name. For example “something_2022-06-20T1722+0000_1655745728_more_text.tbz”