golden hour

/usr/include/c++/11/experimental

File/Folder	Size	Actions
algorithm	3.6 KB
any	15.64 KB
array	3.29 KB
bits	-
buffer	28.05 KB
chrono	1.91 KB
deque	2.24 KB
executor	54.7 KB
filesystem	1.55 KB
forward_list	2.31 KB
functional	12 KB
internet	64.77 KB
io_context	22 KB
iterator	3.45 KB
list	2.21 KB
map	2.53 KB
memory	5.91 KB
memory_resource	17.12 KB
net	1.51 KB
netfwd	3.66 KB
numeric	3.4 KB
optional	25.99 KB
propagate_const	15.13 KB
random	2.51 KB
ratio	2.38 KB
regex	2.07 KB
set	2.41 KB
simd	2.75 KB
socket	76.34 KB
source_location	2.71 KB
string	2.85 KB
string_view	21.99 KB
system_error	2 KB
timer	5.66 KB
tuple	2.41 KB
type_traits	11.78 KB
unordered_map	2.78 KB
unordered_set	2.66 KB
utility	1.69 KB
vector	2.3 KB

Edit: chrono

// Variable Templates For chrono -*- C++ -*-

// Copyright (C) 2014-2021 Free Software Foundation, Inc.
//
// This file is part of the GNU ISO C++ Library.  This library is free
// software; you can redistribute it and/or modify it under the
// terms of the GNU General Public License as published by the
// Free Software Foundation; either version 3, or (at your option)
// any later version.

// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.

// Under Section 7 of GPL version 3, you are granted additional
// permissions described in the GCC Runtime Library Exception, version
// 3.1, as published by the Free Software Foundation.

// You should have received a copy of the GNU General Public License and
// a copy of the GCC Runtime Library Exception along with this program;
// see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
// <http://www.gnu.org/licenses/>.

/** @file experimental/chrono
 *  This is a TS C++ Library header.
 *  @ingroup libfund-ts
 */

//
// N3932 Variable Templates For Type Traits (Revision 1)
//

#ifndef _GLIBCXX_EXPERIMENTAL_CHRONO
#define _GLIBCXX_EXPERIMENTAL_CHRONO 1

#pragma GCC system_header

#if __cplusplus >= 201402L

#include <chrono>
#include <experimental/bits/lfts_config.h>

namespace std _GLIBCXX_VISIBILITY(default)
{
_GLIBCXX_BEGIN_NAMESPACE_VERSION

namespace chrono {
namespace experimental
{
inline namespace fundamentals_v1
{
// See C++14 20.12.4, customization traits
template <typename _Rep>
   constexpr bool treat_as_floating_point_v =
     treat_as_floating_point<_Rep>::value;
} // namespace fundamentals_v1
} // namespace experimental
} // namespace chrono
_GLIBCXX_END_NAMESPACE_VERSION
} // namespace std

#endif // __cplusplus <= 201103L

#endif // _GLIBCXX_EXPERIMENTAL_CHRONO