Split off from where I noticed that da actually has some issues compared to source and other languages:
EEEE, MMMM d, y
EEEE 'den' d. MMMM y
EEEE d. MMMM y
EEEE d MMMM y
MMMM d, y
d. MMM y
d. MMMM y
d MMMM y
MMM d, y
d. MMM y
d MMM y
For Danish, I noted the following:
The long format uses MMM (sep.), whereas English uses MMMM (september). Curious why the short form is used for Danish? It looks like Google wanted the long form (d. MMMM y), but it didn't go through since the short form is the legacy value.'
The medium format for Danish is completely numeric, using MM (09), in contrast to English and the others that uses the abbreviated form (sep.). Again, Google voted to change it to resemble the US format (d. MMM y) but it didn't go through.
The short format becomes a version of the medium format, with the only difference that it's forcing a two-digit year. (It's very possible that the short format became two-digit because that's what English is using, but this is not necessary to follow.)
Our Danish vetter is on vacation right now and couldn't answer these questions. Our other Danish native speaker sees no problem with accepting Google's suggested changes per se, but contends that the short format should use the two-digit year as it's more common.