[Boost-users] linker error when using from_simple_string()

Hello, This line of code: date birthday(from_simple_string(s)); causes this error: Undefined symbols for architecture x86_64: "boost::gregorian::greg_month::get_month_map_ptr()", referenced from: unsigned short boost::date_time::month_str_to_ushortboost::gregorian::greg_month(std::string const&) in boost2-aLwtLt.o ld: symbol(s) not found for architecture x86_64 Any help will be appreciated. Thanks. Regards, Phil