s://wg21.link/P2714R1)  
` __cpp_lib_bit_cast ` |  [ ` std::bit_cast ` ](/w/cpp/numeric/bit_cast "cpp/numeric/bit cast") |  201806L  |  [ ` <bit> ` ](/w/cpp/header/bit "cpp/header/bit") |  (C++20)  |  [ P0476R2 ](https://wg21.link/P0476R2)  
` __cpp_lib_bitops ` |  [ Bit operations ](/w/cpp/numeric#Bit_manipulation_.28since_C.2B.2B20.29 "cpp/numeric") |  201907L  |  [ ` <bit> ` ](/w/cpp/header/bit "cpp/header/bit") |  (C++20)  |  [ P0553R4 ](https://wg21.link/P0553R4)  
` __cpp_lib_bitset ` |  Interfacing  [ std::bitset ](/w/cpp/utility/bitset "cpp/utility/bitset") with  [ std::string_view ](/w/cpp/string/basic_string_view "cpp/string/basic string view") |  202306L  |  [ ` <bitset> ` ](/w/cpp/header/bitset "cpp/header/bitset") |  (C++26)  |  [ P2697R1 ](https://wg21.link/P2697R1)  
` __cpp_lib_bool_constant ` |  [ std::bool_constant ](/w/cpp/types/integral_constant "cpp/types/integral constant") |  201505L  |  [ ` <type_traits> ` ](/w/cpp/header/type_traits "cpp/header/type traits") |  (C++17)  |  [ N4389 ](https://wg21.link/N4389)  
` __cpp_lib_bounded_array_traits ` |  [ ` std::is_bounded_array ` ](/w/cpp/types/is_bounded_array "cpp/types/is bounded array") , [ ` std::is_unbounded_array ` ](/w/cpp/types/is_unbounded_array "cpp/types/is unbounded array") |  201902L  |  [ ` <type_traits> ` ](/w/cpp/header/type_traits "cpp/header/type traits") |  (C++20)  |  [ P1357R1 ](https://wg21.link/P1357R1)  
` __cpp_lib_boyer_moore_searcher ` |  [ Searchers ](/w/cpp/utility/functional#Searchers "cpp/utility/functional") |  201603L  |  [ ` <functional> ` ](/w/cpp/header/functional "cpp/header/functional") |  (C++17)  |  [ P0220R1 ](https://wg21.link/P0220R1)  
` __cpp_lib_byte ` |  [ ` std::byte ` ](/w/cpp/types/byte "cpp/types/byte") |  201603L  |  [ ` <cstddef> ` ](/w/cpp/header/cstddef "cpp/header/cstddef") |  (C++17)  |  [ P0298R3 ](https://wg21.link/P0298R3)  
` __cpp_lib_byteswap ` |  [ ` std::byteswap ` ](/w/cpp/numeric/byteswap "cpp/numeric/byteswap") |  202110L  |  [ ` <bit> ` ](/w/cpp/header/bit "cpp/header/bit") |  (C++23)  |  [ P1272R4 ](https://wg21.link/P1272R4)  
` __cpp_lib_char8_t ` |  Library support for [ ` char8_t ` ](/w/cpp/language/types#char8_t "cpp/language/types") |  201907L  |  [ ` <atomic> ` ](/w/cpp/header/atomic "cpp/header/atomic") [ ` <filesystem> ` ](/w/cpp/header/filesystem "cpp/header/filesystem") [ ` <istream> ` ](/w/cpp/header/istream "cpp/header/istream") [ ` <limits> ` ](/w/cpp/header/limits "cpp/header/limits") [ ` <locale> ` ](/w/cpp/header/locale "cpp/header/locale") [ ` <ostream> ` ](/w/cpp/header/ostream "cpp/header/ostream") [ ` <string> ` ](/w/cpp/header/string "cpp/header/string") [ ` <string_view> ` ](/w/cpp/header/string_view "cpp/header/string view") |  (C++20)  |  [ P0482R6 ](https://wg21.link/P0482R6)   
[ P1423R3 ](https://wg21.link/P1423R3)  
` __cpp_lib_chrono ` |  Rounding functions for  [ std::chrono::duration ](/w/cpp/chrono/duration "cpp/chrono/duration") and  [ std::chrono::time_point ](/w/cpp/chrono/time_point "cpp/chrono/time point") |  201510L  |  [ ` <chrono> ` ](/w/cpp/header/chrono "cpp/header/chrono") |  (C++17)  |  [ P0092R1 ](https://wg21.link/P0092R1)  
Constexpr for all the member functions of  [ std::chrono::duration ](/w/cpp/chrono/duration "cpp/chrono/duration") and  [ std::chrono::time_point ](/w/cpp/chrono/time_point "cpp/chrono/time point") |  201611L  |  [ ` <chrono> ` ](/w/cpp/header/chrono "cpp/header/chrono") |  (C++17)  |  [ P0505R0 ](https://wg21.link/P0505R0)  
[ Calendars ](/w/cpp/chrono#Calendar "cpp/chrono") and [ Time Zones ](/w/cpp/chrono#Time_zone "cpp/chrono") |  201907L  |  [ ` <chrono> ` ](/w/cpp/header/chrono "cpp/header/chrono") |  (C++20)  |  [ P0355R7 ](https://wg21.link/P0355R7)   
[ P1466R3 ](https://wg21.link/P1466R3)  
[ Hashing ](/w/cpp/utility/hash "cpp/utility/hash") support for [ ` std::chrono ` ](/w/cpp/chrono "cpp/chrono") value classes  |  202306L  |  [ ` <chrono> ` ](/w/cpp/header/chrono "cpp/header/chrono") |  (C++26)  |  [ P2592R3