helps‎ > ‎

set locale/time

set new default locale

dpkg-reconfigure locales

find the locale to add -usually you want UTF-8 -listed here
hit Space bar and Enter

or manually, 
sudo nano /etc/locale.gen
and uncomment the languages you need (delete #), then Ctrl-X, y enter

sudo locale-gen xx_YY.UTF-8

to set your default language
sudo nano /etc/default/locale
change content to 
and save (replace x and Y with your language to be default for system)
or try sudo update-locale xx_YY.UTF-8

after any changes you must run

then log out and back in

UTC time and Debian's clock
If the BIOS clock is local time, and debian's clock is shifted to what it thinks is local time, because it thinks that hardware clock is set to UTC.
The method to edit /etc/default/rcS, with "UTC=no" hasn't ever worked for me.  Following Debian Wiki, we must edit /etc/adjtime,

sudo nano /etc/adjtime
change "UTC" to "LOCAL"
Ctrl-X, y enter

does it work ??
failing that, enter your BIOS and adjust the time back/forward to UTC time, so that Debian adds hours for your time-zone and the displayed time will be correct

You can set your time-zone with
sudo dpkg-reconfigure tzdata

update the time with ntp
you can have the system time updated by a network time protocol by installing ntp
sudo apt-get install ntp

the ntp daemon will update you Debian clock constantly, if there is a constant internet conection.
If the connection is not constant, you can run
ntpd -b
to update the clock once you have internet