std::chrono::weekday:: c_encoding, std::chrono::weekday:: iso_encoding

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C-style date and time
std::chrono::weekday
constexpr unsigned c_encoding ( ) const noexcept ;
(1) (since C++20)
constexpr unsigned iso_encoding ( ) const noexcept ;
(2) (since C++20)
1) Returns the weekday value stored in * this .
2) Returns the weekday value stored in * this , except that Sunday (stored as ​ 0 ​ ) is interpreted as 7 according to ISO 8601.

Return value

1) The weekday value stored in * this .
2) c_encoding ( ) == 0u ? 7u : c_encoding ( )

Example

Run this code 
#include <chrono>
#include <iostream>
 
int main()
{
    std::cout << "i: C: ISO: Weekday:\n";
 
    for (unsigned i{0}; i != 8; ++i)
    {
        const std::chrono::weekday w{i};
        std::cout << i << "  "
                  << w.c_encoding() << "  "
                  << w.iso_encoding() << "    "
                  << w << '\n';
    }
}

Output: 

i: C: ISO: Weekday:
0  0  7    Sun
1  1  1    Mon
2  2  2    Tue
3  3  3    Wed
4  4  4    Thu
5  5  5    Fri
6  6  6    Sat
7  0  7    Sun
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