std::chrono::year:: is_leap

* this が 先発グレゴリオ暦 における閏年を表すかどうかを判定します。

* this 格納された年の値が閏年を表す場合

• 4で割り切れ、かつ100で割り切れない場合；または
• 400で割り切れる場合。

戻り値

true が * this が閏年を表す場合、そうでない場合は false を返します。

例

#include <chrono>
#include <iostream>
int main()
{
    using namespace std::chrono_literals;
    for (const std::chrono::year y : {2020y, 2021y, 2000y, 3000y})
    {
        if (const int iy{static_cast<int>(y)}; y.is_leap())
            std::cout << iy << " is a leap year because it is divisible by "
                      << (iy % 400 == 0 ? "400\n" : "4 and not divisible by 100\n");
        else
            std::cout << iy << " is not a leap year\n";
    }
}

2020 is a leap year because it is divisible by 4 and not divisible by 100
2021 is not a leap year
2000 is a leap year because it is divisible by 400
3000 is not a leap year