FWCalendar is localized for several languages (currently English, German, Swedish, Italian, Spanish, French, Norsk, and Portugese) by including the proper translations for month names, weekday names, and requester strings in the preferences file. Not speaking any of these languages other than English, I relied on help from people using these macros or used the translation utility available from Alta Vista to translate the weekdays, months, New Year's Day, and Christmas. Without your help, I have no way of confirming the accuracy of these translations.
In addition to New Year's Day and Christmas, national holidays or celebration days are listed for many countries: America, England, France, Germany, Ireland, Italy, Norway, Scotland, Spain, and Sweden. Much of the information for this area was obtained from The Worldwide Holiday & Festival Site. I would appreciate your contributions for other countries. Please email me the "highlights" for your country and I will update the available preferences files.
To see the variables that can be localized, look at the variables.