cpp_20_calendar.hpp

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#pragma once
 
/// @file userver/utils/datetime/cpp_20_calendar.hpp
/// @brief This file brings date.h into utils::datetime::date namespace,
/// which is std::chrono::operator/ (calendar) in c++20.
/// @ingroup userver_universal
 
// TODO : replace with C++20 std::chrono:: when time comes
 
#include <chrono>
#include <ratio>
 
#include <date/date.h>
 
#include <userver/utils/assert.hpp>
 
USERVER_NAMESPACE_BEGIN
 
namespace utils::datetime {
 
namespace date = ::date;
 
using Days = date::days;
using DaysTimepoint = date::sys_days;
 
/// @brief Calculates the number of days between January 1, 00:00 of two years accounting for leap years.
constexpr Days DaysBetweenYears(int from, int to) {
    return std::chrono::duration_cast<Days>(
        DaysTimepoint{date::year_month_day(date::year(to), date::month(1), date::day(1))} -
        DaysTimepoint{date::year_month_day(date::year(from), date::month(1), date::day(1))}
    );
}
 
/// @brief Get the number of days in the given month of a given year.
constexpr date::day DaysInMonth(int month, int year) {
    UINVARIANT(month >= 1 && month <= 12, "Month must be between 1 and 12");
    return date::year_month_day_last(date::year(year), date::month_day_last(date::month(month))).day();
}
 
}  // namespace utils::datetime
 
USERVER_NAMESPACE_END