I've set all locale tabs for my country except language which is English and i like to keep it that way, the only thing i don't like is that weekdays and months are also in English. I've also noticed that on login screen time is in 12h format instead of 24h. So i wondering is it possible to change language for time and date related stuff and how?

To get a 12 Hour clock format, open System Settings > Locale > Country, Region & Language > Date & Time. Ensure "pH:MM:SS AMPM" is set for "Time format".

In terms of the language used for month and day names - i'm not sure this can be changed independently i'm afraid.

bcooksley wrote:To get a 12 Hour clock format, open System Settings > Locale > Country, Region & Language > Date & Time. Ensure "pH:MM:SS AMPM" is set for "Time format".

I wasn't clear enough, i want a 24 Hour format and i already works well with clock on bottom right corner of the screen, the thing is that on login screen time is shown in 12 Hour format... I don't know if the clock is a standard login screen element or is it a theme custom element though...

bcooksley wrote:In terms of the language used for month and day names - i'm not sure this can be changed independently i'm afraid.

I was asking because Windows choose clock language based on locale settings and not on system wide language. I've tried changing locale enviroment variable LC_TIME to another locale in hope that it will change time language but it did nothing.

Assumingly viewtopic.php?f=66&t=91784 ?

KDE has it's own translation system, so I suspect LC_* will not have an impact in this case.
In regards to the KDM clock format - that thread luebking posted above appears to be relevant to your situation.