chrono / calendar

Create a function called getAgeInYears that expects the dayOfBirth as parameter and returns the age in year (with day precision)

Info

The current compiler version does not include all chrono featured yet, so you have to use the header <date/date.h> installed from https://github.com/HowardHinnant/date

Solution

#include <iostream>
#include <date/date.h>

int getAgeInYears(date::year_month_day dayOfBirth) {
    // timestamp
    auto now = std::chrono::system_clock::now();
    // convert to sys_days
    date::sys_days nowSysDays = date::floor<date::days>(now);
    // convert to year_month_day (same as dayOfBirth)
    date::year_month_day nowYmd = date::year_month_day{nowSysDays};
    auto ageInDays = date::local_days{nowYmd} - date::local_days{dayOfBirth};
    date::years ageInYears = std::chrono::duration_cast<date::years>(ageInDays);
    return ageInYears.count();
}

int main()
{
    using namespace date;
    constexpr auto x1 = 1981_y/March/11;
    constexpr auto x2 = October/07/1991;
    constexpr auto x3 = 26_d/October/2015;
    std::cout << "You are " << getAgeInYears(x1) << " years old\n";
    std::cout << "You are " << getAgeInYears(x2) << " years old\n";
    std::cout << "You are " << getAgeInYears(x3) << " years old\n";
    return 0;
}

Links

https://en.cppreference.com/w/cpp/chrono https://github.com/HowardHinnant/date