year_month_day class

Represents a month, year, and day.

Syntax

class year_month_day; // C++20

Members

Name	Description
Constructors	Construct a year_month_day
day	Returns the day.
month	Returns the month.
ok	Verify that the year and month values are in the valid range.
operator+=	Add the specified number of months or years.
operator-=	Subtract the specified number of months or years.
operator local_days	Get the count of days from the system_clock epoch to this year_month_day as local_days.
operator sys_days	Get the count of days from the system_clock epoch to this year_month_day as sys_days.
year	Returns the year.

Non-members

Name	Description
from_stream	Parse a year_month_day from a stream using the specified format
operator+	Add months or years.
operator-	Subtract months or years.
operator==	Determine whether two year_month_day values are equal.
operator<=>	Compare two year_month_day values. The >, >=, <=, <, != operators are synthesized by the compiler.
operator<<	Output a year_month_day to a stream.

Requirements

Header: <chrono> (since C++20)

Namespace: std::chrono

Compiler Option: /std:c++latest

Constructors

Construct a year_month_day.

1) year_month_day() = default;
2) constexpr year_month_day(const year& y, const month& m, day& d) noexcept;
3) constexpr year_month_day(const year_month_day_last& ymdl) noexcept;
4) constexpr year_month_day(const sys_days& dp) noexcept;
5) constexpr explicit year_month_day(const local_days& dp) noexcept;

Parameters

d A day value.

dp A sys_days or local_days value.

m A month value.

y
A year value.

ymdl A year_month_day_last value.

Remarks

1) The default constructor doesn't initialize the month or day.
2) Constructs a year_month_daywith the specified year, month, and day.
3) Constructs a year_month_daywith the specified year, month, and day from ymdl
4) Constructs a year_month_daywith the same date as dp.
5) Constructs a year_month_daywith the same date as dp but as though constructed by year_month_day(sys_days(dp.time_since_epoch())).

For information about C++20 syntax used to specify dates, see operator/

Example: Create a year_month_day

// compile using: /std:c++latest
#include <iostream>
#include <chrono>

using namespace std::chrono;

int main()
{
    year_month_day ymd{ April / 4 / 1975 };
    std::cout << ymd;
    return 0;
}

1975-04-04

day

Get the day.

constexpr day day() const noexcept;

Return value

The day value.

month

Get the month.

constexpr month month() const noexcept;

Return value

The month value.

operator local_days

Get the count of days from the system_clock epoch (1/1/1970) to this year_month_day as local_days

constexpr explicit operator local_days() const noexcept;

Return value

If ok(), returns a count of days as local_days{sys_days{*this}.time_since_epoch()}

operator sys_days

Get the count of days from the system_clock epoch (1/1/1970) to this year_month_day as sys_days.

constexpr operator sys_days() const noexcept;

Return value

If ok(), returns a sys_days holding a count of days from the sys_days epoch (1/1/1970) to the date held in this year_month_day. The value will be negative if the date in this year_month_day is prior to the sys_days epoch.

If the year and month in this year_month_day are ok(), returns sys_days{year/month/1d} + (day-1d). Otherwise the value returned is unspecified.

A sys_days in the range [days{-12687428}, days{11248737}] can be converted to a year_month_day and back and have have the same value.

year

Get the year.

constexpr year year() const noexcept;

Return value

The year.

ok

Check if the year and month value stored in this year_month_day are both in the valid range. Ensures that the day is in the range [1d, (y/m/last).day()], accounting for leap years and the different number of days in each month.

constexpr bool ok() const noexcept;

Return value

true if the year_month_day year, month, and day values are in the valid range. Otherwise, false.

operator+=

Add months or years to this year_month_day.

1) constexpr year_month_day& operator+=(const months& dm) noexcept;
2) constexpr year_month_day& operator+=(const years& dy) noexcept;

Parameters

dm
The number of months to add.

dy
The number of years to add.

Return value

*this, which reflects the result of the addition.

Example: operator+=

// compile using: /std:c++latest
#include <iostream>
#include <chrono>

using namespace std::chrono;

int main()
{
    year_month_day ymd{June / 1d / 2021y};

    std::cout << ymd << '\n';

    ymd += months{2};
    ymd += years{1};

    std::cout << ymd;
    
    return 0;
}

2021-06-01
2022-08-01

operator-=

Subtract months or years from this year_month_day.

1) constexpr year_month_day& operator-=(const months& dm) noexcept;
2) constexpr year_month_day& operator-=(const years& dy) noexcept;

Parameters

dm
The number of months to subtract.

dy
The number of years to subtract.

Return value

*this, which reflects the result of the subtraction.

Example: operator-=

// compile using: /std:c++latest
#include <iostream>
#include <chrono>

using namespace std::chrono;

int main()
{
    year_month_day ymd{June / 1d / 2021y};

    std::cout << ymd << '\n';

    ymd -= months{2};
    ymd -= years{1};

    std::cout << ymd;
    
    return 0;
}

2021-06-01
2020-04-01

See also

<chrono>
year
year_month
year_month_day_last
year_month_weekday
year_month_weekday_last
operator/
Header Files Reference