Set locale time

set new default locale

as root, run

dpkg-reconfigure locales

find the locale to add -usually you want UTF-8 (listed herehttp://www.science.co.il/...)

hit Space bar to select each one and then hit Enter

or manually,

sudo nano/etc/locale.gen

and uncomment the languages you need (delete #), then Ctrl-X, y Enter

or use a command like..

sudo locale-genxx_YY.UTF-8

to set your default language

sudo nano /etc/default/locale

change content to

LANG=xx_YY.UTF-8

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

locale-gen

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" then Ctrl-X, y enter

but does it work ??

failing that, you should try ntp (see below) or you can 'fix' your BIOS clock 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 install ntp

the ntp daemon will update your 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

update the time with hwclock

in case you are out of internet service for a long while, you can set the hardware clock with the hwclock command, e.g.:

sudo hwclock --set --date='2017-11-23 15:19:40'