This end user SharePoint Tutorial shows how to change the regional settings of a SharePoint site. This affects e.g. date and time in a SharePoint calendar.
SharePoint is used around the world and different countries have different languages and a different usage of numbers, time or dates. SharePoint supports "different types of regional settings: locale, time zone, sort order, calendar, and currency". As far as I know there is no difference between SharePoint Foundation and SharePoint Server.
The installation of language packs is not required for the configuration of regional settings in a SharePoint site.
How to change regional settings of a SharePoint site
Changing the regional settings of a site affects things like the calender dates and times, currency and numerics. In order to change the regional settings you need to open site settings and click on regional settings under the site administration group.
If you have the "Office Sharepoint Server Publishing" feature activated you will find a checkbox to inherit the settings to all sub sites.
As a SharePoint administrator you can set regional settings at Web Application level so that each site which is created after the change will reflect the new settings.
As a SharePoint user you can click on your login name to open "My settings" which allows you to set your own regional settings.