Time and date format

Hello, 

is it possible to set time and date format according to user's preference? We use carbonio in English, because it is not translated to Czech or Slovak language, but we'd like to at least have the 24-hour time instead of AM/PM, and date in D. M. YYYY or at least YYYY/MM/DD. 

What is even more interesting, some users have the local time/dat format, and some have the american format. We have migrated from zimbra, so maybe some preferences were preserved? Is it possible to add at least the time/date formatting to be selectable without fixed dependency on the language?

Thanks

Vladki