![\"TimelineCpp20CoreLanguage\"](\"https:\/\/www.modernescpp.com\/wp-content\/uploads\/2020\/07\/TimelineCpp20CoreLanguage.png\")
<\/p>\nA new type of the chrono extension in C++20 is a calendar date. C++20 offers various ways to create a calendar date and interact with them.<\/p>\n
<\/p>\n
<\/p>\n
<\/p>\n
It took me a while to understand the almost twenty calendar-related data types. For that reason, I start with a calendar date. As in my last post, “Calendar and Time-Zones in C++20: Time of Day<\/a> “, I use the date <\/a>library from Howard Hinnant as the prototype of the new chrono <\/a>extension.<\/p>\n <\/p>\n A calendar date is a date that consists of a year, a month, and a day. Consequently, C++20 has a specific data type <\/p>\n Let’s start simple. The following program <\/p>\n <\/p>\n <\/p>\n There are essentially two ways to create a calendar date. You can use the so-called cute syntax Line (3), line (4), and line (5) offer convenient ways to create calendar dates.<\/p>\n The remaining calendar types stand for a day (line 6), a month (line 7), or a year (line 8). You can combine them as basic building blocks for fully specified calendar dates, such as lines (3) to (4).<\/p>\n Before I dive more into the details, here is the program’s output. As promised, let me write about the cute syntax.<\/p>\n The cute syntax consists of overloaded division operators to specify a calendar date. The overloaded operators support time literals (e.g.: The following three combinations of year, month, and day are possible using the cute syntax.<\/p>\n These combinations are not arbitrarily chosen because they are the used ones worldwide. Each other combination is not allowed<\/p>\n Consequently, when you choose the type year, month, or day for the first argument, the type for the remaining two arguments is no longer necessary, and an integral would do the job.<\/p>\n <\/p>\n <\/p>\nCalendar Date<\/h2>\n
std::chrono::year_month_day<\/code>. C++20 has way more to offer. Both tables present the first overview.<\/p>\n![\"calendar1\"](\"https:\/\/www.modernescpp.com\/wp-content\/uploads\/2020\/11\/calendar1.PNG\")
<\/p>\n![\"calendar2\"](\"https:\/\/www.modernescpp.com\/wp-content\/uploads\/2020\/11\/calendar2.PNG\")
<\/p>\n createCalendar.cpp<\/code> shows various ways to create calendar-related dates.<\/p>\n\n\/\/ createCalendar.cpp<\/span>\r\n\r\n#include <iostream><\/span>\r\n#include \"date.h\"<\/span>\r\n \r\nint<\/span> main<\/span>() {\r\n\r\n std::<\/span>cout <<<\/span> std::<\/span>endl;\r\n \r\n using<\/span> namespace<\/span> date;\r\n\r\n constexpr auto<\/span> yearMonthDay{year(1940<\/span>)\/<\/span>month(6<\/span>)\/<\/span>day(26<\/span>)}; \/\/ (1)<\/span>\r\n std::<\/span>cout <<<\/span> yearMonthDay <<<\/span> \" \"<\/span>;\r\n std::<\/span>cout <<<\/span> date::<\/span>year_month_day(1940<\/span>_y, June, 26<\/span>_d) <<<\/span> std::<\/span>endl; \/\/ (2)<\/span>\r\n\r\n std::<\/span>cout <<<\/span> std::<\/span>endl;\r\n\r\n constexpr auto<\/span> yearMonthDayLast{year(2010<\/span>)\/<\/span>March\/<\/span>last}; \/\/ (3)<\/span>\r\n std::<\/span>cout <<<\/span> yearMonthDayLast <<<\/span> \" \"<\/span>;\r\n std::<\/span>cout <<<\/span> date::<\/span>year_month_day_last(2010<\/span>_y, month_day_last(month(3<\/span>))) <<<\/span> std::<\/span>endl;\r\n\r\n constexpr auto<\/span> yearMonthWeekday{year(2020<\/span>)\/<\/span>March\/<\/span>Thursday[2<\/span>]}; \/\/ (4)<\/span>\r\n std::<\/span>cout <<<\/span> yearMonthWeekday <<<\/span> \" \"<\/span>;\r\n std::<\/span>cout <<<\/span> date::<\/span>year_month_weekday(2020<\/span>_y, month(March), Thursday[2<\/span>]) <<<\/span> std::<\/span>endl;\r\n\r\n constexpr auto<\/span> yearMonthWeekdayLast{year(2010<\/span>)\/<\/span>March\/<\/span>Monday[last]}; \/\/ (5)<\/span>\r\n std::<\/span>cout <<<\/span> yearMonthWeekdayLast <<<\/span> \" \"<\/span>;\r\n std::<\/span>cout <<<\/span> date::<\/span>year_month_weekday_last(2010<\/span>_y, month(March), weekday_last(Monday)) <<<\/span> std::<\/span>endl;\r\n\r\n std::<\/span>cout <<<\/span> std::<\/span>endl;\r\n\r\n constexpr auto<\/span> day_{day(19<\/span>)}; \/\/ (5)<\/span>\r\n std::<\/span>cout <<<\/span> day_ <<<\/span> \" \"<\/span>;\r\n std::<\/span>cout <<<\/span> date::<\/span>day(19<\/span>) <<<\/span> std::<\/span>endl;\r\n\r\n constexpr auto<\/span> month_{month(1<\/span>)}; \/\/ (6)<\/span>\r\n std::<\/span>cout <<<\/span> month_ <<<\/span> \" \"<\/span>;\r\n std::<\/span>cout <<<\/span> date::<\/span>month(1<\/span>) <<<\/span> std::<\/span>endl;\r\n\r\n constexpr auto<\/span> year_{year(1988<\/span>)}; \/\/ (7)<\/span>\r\n std::<\/span>cout <<<\/span> year_ <<<\/span> \" \"<\/span>;\r\n std::<\/span>cout <<<\/span> date::<\/span>year(1988<\/span>) <<<\/span> std::<\/span>endl;\r\n\r\n constexpr auto<\/span> weekday_{weekday(5<\/span>)};\r\n std::<\/span>cout <<<\/span> weekday_ <<<\/span> \" \"<\/span>;\r\n std::<\/span>cout <<<\/span> date::<\/span>weekday(5<\/span>) <<<\/span> std::<\/span>endl;\r\n \r\n constexpr auto<\/span> yearMonth{year(1988<\/span>)\/<\/span>1<\/span>};\r\n std::<\/span>cout <<<\/span> yearMonth <<<\/span> \" \"<\/span>;\r\n std::<\/span>cout <<<\/span> date::<\/span>year_month(year(1988<\/span>), January) <<<\/span> std::<\/span>endl;\r\n \r\n constexpr auto<\/span> monthDay{10<\/span>\/<\/span>day(22<\/span>)};\r\n std::<\/span>cout <<<\/span> monthDay <<<\/span> \" \"<\/span>;\r\n std::<\/span>cout <<<\/span> date::<\/span>month_day(October, day(22<\/span>)) <<<\/span> std::<\/span>endl;\r\n\r\n constexpr auto<\/span> monthDayLast{June\/<\/span>last};\r\n std::<\/span>cout <<<\/span> monthDayLast <<<\/span> \" \"<\/span>;\r\n std::<\/span>cout <<<\/span> date::<\/span>month_day_last(month(6<\/span>)) <<<\/span> std::<\/span>endl;\r\n \r\n constexpr auto<\/span> monthWeekday{2<\/span>\/<\/span>Monday[3<\/span>]};\r\n std::<\/span>cout <<<\/span> monthWeekday <<<\/span> \" \"<\/span>;\r\n std::<\/span>cout <<<\/span> date::<\/span>month_weekday(February, Monday[3<\/span>]) <<<\/span> std::<\/span>endl;\r\n \r\n constexpr auto<\/span> monthWeekDayLast{June\/<\/span>Sunday[last]};\r\n std::<\/span>cout <<<\/span> monthWeekDayLast <<<\/span> \" \"<\/span>;\r\n std::<\/span>cout <<<\/span> date::<\/span>month_weekday_last(June, weekday_last(Sunday)) <<<\/span> std::<\/span>endl;\r\n\r\n std::<\/span>cout <<<\/span> std::<\/span>endl;\r\n\r\n}\r\n<\/pre>\n<\/div>\n yearMonthDay{year(1940)\/month(6)\/day(26)}<\/code> (line 1), or you can use the explicit type date::year_month_day(1940_y, June, 26_d)<\/code> (line 2). To not overwhelm you, I am delaying my explanation of the cute syntax to the next section of this post. The explicit type is quite interesting because it uses the date <\/a>time literals 1940_y, 26_d, and the predefined constant June<\/code>. With C++20, the date literals 1940_y<\/code> and 26_d<\/code> are written without an underscore: 1940y<\/code> and 26d<\/code>. This was the prominent part.
<\/span><\/p>\n\n
{year(2010)\/March\/last}<\/code> or year_month_day_last(2010_y, month_day_last(month(3))<\/code><\/li>\n{year(2020)\/March\/Thursday[2]}<\/code> or year_month_weekday(2020_y, month(March), Thursday[2])<\/code><\/li>\nyear_month_weekday_last(2010_y, month(March), weekday_last(Monday))<\/code><\/li>\n<\/ul>\n
<\/span><\/p>\n![\"calendarDate\"](\"https:\/\/www.modernescpp.com\/wp-content\/uploads\/2020\/11\/calendarDate.png\")
<\/p>\nCute Syntax<\/h3>\n
2020_y, 31_d<\/code>) and constants (January, February, March, April, May, June, July, August, September, October, November, December<\/code>).<\/p>\n\n
\n\/\/ cuteSyntax.cpp<\/span>\r\n\r\n#include <iostream><\/span>\r\n#include \"date.h\"<\/span>\r\n\r\nint<\/span> main<\/span>() {\r\n\r\n std::<\/span>cout <<<\/span> std::<\/span>endl;\r\n\r\n using<\/span> namespace<\/span> date;\r\n\r\n constexpr auto<\/span> yearMonthDay{year(1966<\/span>)\/<\/span>6<\/span>\/<\/span>26<\/span>};\r\n std