Other than implementing the ISO standard alternate language .. I can only assume that you're wanting to override how the en-US language (select * from nop_Language) implements dates.
It seems that you could easily add a new Locale String Resource:
insert into Nop_LocaleStringResource (LanguageID, ResourceName, ResourceValue)
values (7, 'Admin.GlobalSettings.Date.Format', 'dddd, dd MMMM yyyy')
and get that object wrapped so you could update where dates are used (the one I found was in the order form control of /Modules/OrderDetails.ascx.cs
this.lblCreatedOn.Text = DateTimeHelper.ConvertToUserTime(order.CreatedOn).ToString("D");
You could change this to reflect the new locale string resource value or just manually alter it to be:
this.lblCreatedOn.Text = DateTimeHelper.ConvertToUserTime(order.CreatedOn).ToString("dddd, dd MMMM yyyy");
Maybe that points you in the right direction. Date handling should be added as a permanent addition to the locale string resource collections in future versions. Been doing international tennis websites and we run into this all the time... not doing commerce sites for that yet so I haven't had to mash up NOP Commerce.
Thanks,
Jared Nielsen
www.FUZION.org