First of all, you need to add a reference manually to sysglobl.dll.
sysglobl.dll is a very tiny assembly. It contains only one class CultureAndRegionInfoBuilder
Include the namespace System.Globalization.
Add the following code snippet written in C# for achieving it…..
string UserSystemLocale = System.Globalization.CultureInfo.InstalledUICulture.ToString(); string CurrentSiteLocale = web.Locale.ToString(); using (SPSite site = new SPSite("site url")) { try { using (SPWeb web = site.OpenWeb()) { if (web != null) { web.AllowUnsafeUpdates = true; try { CultureAndRegionInfoBuilder.Unregister(CurrentSiteLocale); } catch(Exception ex) { // Log exception } CultureAndRegionInfoBuilder carib = new CultureAndRegionInfoBuilder(CurrentSiteLocale, CultureAndRegionModifiers.Replacement); carib.LoadDataFromCultureInfo(new CultureInfo(UserSystemLocale)); carib.LoadDataFromRegionInfo(new RegionInfo(UserSystemLocale)); carib.Register(); CultureInfo ci = new CultureInfo(UserSystemLocale); web.Locale = ci; web.Update(); web.AllowUnsafeUpdates = false; } } } catch (Exception ex) { // Log exception } }