Road trip day tiles still wrote numeric dates from the clock setting and
dates in the medium style kept the language's numbers. A poll deadline
whose time was cleared was read as UTC midnight.
Every date in TREK was written in the interface language's format, and
English is en-US, so an English interface always showed and read
mm/dd/yyyy with no way to change it. A few native date inputs followed
the browser instead, so one screen could mix two formats.
date_format is now a user setting with an admin default, next to the
time format: automatic (the language's format, as before), YYYY-MM-DD,
YYYY/MM/DD, DD.MM.YYYY, DD/MM/YYYY or MM/DD/YYYY. The date picker shows,
pre-fills, hints and reads typed dates in it, and every date written in
numbers across the app (lists, cards, admin panels, CSV and PDF exports)
goes through one formatter. Dates written with a month name keep the
language's wording. The remaining native date inputs are the shared
picker now. The display settings MCP tool reads and writes the key.
Closes#2971
Maurice