According to the PostgreSQL 9.5 documentation, LC_TIME affects "Formatting of dates and times" and LC_NUMERIC - "Formatting of numbers", but I can't seem to see any difference from changing these.
For instance, I changed my postgresql.conf to this:
lc_messages = 'English_United States.1252' lc_monetary = 'English_United States.1252' lc_numeric = 'English_United States.1252' lc_time = 'English_United States.1252'
then created a new DB and ran:
SELECT current_date, format('Date: %s, Number: %s', current_date, 1234.6789);
2016-04-26 Date: 2016-04-26, Number: 1234.6789
I then tried the same with "French_France.1252" and "C" collations and got exactly the same results. (I restarted PostgreSQL in-between and verified the changes using
SELECT * FROM pg_settings WHERE name ~~ 'lc%')
So what difference are those settings supposed to make?
I'm running PostgreSQL 9.5.2 on Windows 7.