25 Localization library [localization]

25.2 Header <locale> synopsis [locale.syn]

namespace std {
  // [locale], locale
  class locale;
  template <class Facet> const Facet& use_facet(const locale&);
  template <class Facet> bool         has_facet(const locale&) noexcept;

  // [locale.convenience], convenience interfaces
  template <class charT> bool isspace (charT c, const locale& loc);
  template <class charT> bool isprint (charT c, const locale& loc);
  template <class charT> bool iscntrl (charT c, const locale& loc);
  template <class charT> bool isupper (charT c, const locale& loc);
  template <class charT> bool islower (charT c, const locale& loc);
  template <class charT> bool isalpha (charT c, const locale& loc);
  template <class charT> bool isdigit (charT c, const locale& loc);
  template <class charT> bool ispunct (charT c, const locale& loc);
  template <class charT> bool isxdigit(charT c, const locale& loc);
  template <class charT> bool isalnum (charT c, const locale& loc);
  template <class charT> bool isgraph (charT c, const locale& loc);
  template <class charT> bool isblank (charT c, const locale& loc);
  template <class charT> charT toupper(charT c, const locale& loc);
  template <class charT> charT tolower(charT c, const locale& loc);

  // [category.ctype], ctype
  class ctype_base;
  template <class charT> class ctype;
  template <>            class ctype<char>;     // specialization
  template <class charT> class ctype_byname;
  class codecvt_base;
  template <class internT, class externT, class stateT> class codecvt;
  template <class internT, class externT, class stateT> class codecvt_byname;

  // [category.numeric], numeric
  template <class charT, class InputIterator = istreambuf_iterator<charT>>
    class num_get;
  template <class charT, class OutputIterator = ostreambuf_iterator<charT>>
    class num_put;
  template <class charT>
    class numpunct;
  template <class charT>
    class numpunct_byname;

  // [category.collate], collation
  template <class charT> class collate;
  template <class charT> class collate_byname;

  // [category.time], date and time
  class time_base;
  template <class charT, class InputIterator = istreambuf_iterator<charT>>
    class time_get;
  template <class charT, class InputIterator = istreambuf_iterator<charT>>
    class time_get_byname;
  template <class charT, class OutputIterator = ostreambuf_iterator<charT>>
    class time_put;
  template <class charT, class OutputIterator = ostreambuf_iterator<charT>>
    class time_put_byname;

  // [category.monetary], money
  class money_base;
  template <class charT, class InputIterator = istreambuf_iterator<charT>>
    class money_get;
  template <class charT, class OutputIterator = ostreambuf_iterator<charT>>
    class money_put;
  template <class charT, bool Intl = false>
    class moneypunct;
  template <class charT, bool Intl = false>
    class moneypunct_byname;

  // [category.messages], message retrieval
  class messages_base;
  template <class charT> class messages;
  template <class charT> class messages_byname;
}
The header <locale> defines classes and declares functions that encapsulate and manipulate the information peculiar to a locale.230
In this subclause, the type name struct tm is an incomplete type that is defined in <ctime>.