14.04 - Different UI language for week/month from default in KDE

I would like to have UI in English but week/month names in another language (lets say French, Spanish, Italian ,etc.)

Seems like when I set UI to English, there is no control on week/month names. I just can change calendar type and other similar settings.

This type of settings is extremely useful if your native language is not English, but you prefer to have UI in english.

I am suing KDE in Ubuntu 14.04

Update:

after running sudo update-locale LC_TIME=it_IT.UTF-8

I receive this error:

perl: warning: Setting locale failed.
perl: warning: Please check that your locale settings:
        LANGUAGE = "en:it:fr:en",
        LC_ALL = (unset),
        LC_PAPER = "en_IT.UTF-8",
        LC_ADDRESS = "en_IT.UTF-8",
        LC_MONETARY = "en_IT.UTF-8",
        LC_NUMERIC = "en_IT.UTF-8",

        LC_TELEPHONE = "en_IT.UTF-8",
        LC_IDENTIFICATION = "en_IT.UTF-8",
        LC_MEASUREMENT = "en_IT.UTF-8",
        LC_TIME = "en_IT.UTF-8",
        LC_NAME = "en_IT.UTF-8",
        LANG = "en_IT.UTF-8"
    are supported and installed on your system.
perl: warning: Falling back to the standard locale ("C").

Update 2:
output of local -a (now I dont have French language selected in options any more)

locale: Cannot set LC_CTYPE to default locale: No such file or directory
locale: Cannot set LC_MESSAGES to default locale: No such file or directory
locale: Cannot set LC_COLLATE to default locale: No such file or directory
C
C.UTF-8
POSIX
en_AG

en_AG.utf8
en_AU.utf8
en_BW.utf8
en_CA.utf8
en_DK.utf8
en_GB.utf8
en_HK.utf8
en_IE.utf8
en_IN
en_IN.utf8

en_NG
en_NG.utf8
en_NZ.utf8
en_PH.utf8
en_SG.utf8
en_US.utf8
en_ZA.utf8
en_ZM
en_ZM.utf8
en_ZW.utf8

it_CH.utf8
it_IT.utf8

Week and month names in calendars are usually controlled by the LC_TIME environment variable, so you need to change that. This command sets/changes LC_TIME in the /etc/default/locale file:

sudo update-locale LC_TIME=fr_FR.UTF-8

At next login, weeks/months will hopefully be displayed in French.

Edit: The Problem is related to this bug. As suggested inside the comments, changing the default language to British English fix the issue.
Also more or less the same problem is discussed here.