The GetLocale function returns the LCID (locale ID).

The LCID is a short string, decimal value, or hex value that uniquely identifies a geographic locale. The various geographic locales are based upon the user's language, country, and culture. For example, the locale "English - United States" can be designated as either "en-us", or "1033", or "0x0409".

This locale information is used to establish user preferences and formats for such things as alphabets, currency, dates, keyboard layout, and numbers,

Code:
<% =GetLocale() %>

Output:
1033