[Bug libstdc++/97613] chrono::year_month_weekday cast to sys_days : return bad value if index() == 0

[faithandbrave at gmail dot com via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97613

--- Comment #1 from Akira Takahashi <faithandbrave at gmail dot com> ---
- #include <iostream>
+ #include <cassert>

#include <cassert>
#include <chrono>

namespace chrono = std::chrono;
using namespace std::chrono_literals;

int main()
{
  chrono::sys_days date1 = 2020y/3/chrono::Sunday[1];
  assert(chrono::year_month_day{date1} == 2020y/3/1);

  chrono::sys_days date2 = 2020y/3/chrono::Sunday[2];
  assert(chrono::year_month_day{date2} == 2020y/3/8);

  chrono::sys_days date3 = 2020y/3/chrono::Sunday[0];
  assert(chrono::year_month_day{date3} == 2020y/2/23);
}