如何将 chrono::year_month_day 添加到 chrono::sys_seconds

Question

Am holding duration's in a year_month_day. Is there a simple way to add the year_month_day duration to a time_point like sys_seconds?

sys_seconds date1 = {};
sys_seconds dat2 = {};
year_month_day calDuration;
date1 = date2 + calDuration;    //error: no match for ‘operator+’ 

Answer 1

This is chrono catching logic bugs for you at compile-time. Adding date2 + calDuration is akin to adding tomorrow + today. It just doesn't make sense. And that's why it is a compile-time error.

What you may mean is that you have durations years , months and days . This is not the same as the similarly named types year , month and day . The plural forms are chrono::duration s, just like minutes and nanoseconds . days is 24h . And years and months are the average length of those units in the civil calendar.

Conversely, the singular forms year , month and day are the calendrical components that give a name to a day in the civil calendar, eg 2020y , December , and 18d . And it is these singular forms that make up a year_month_day , eg 2020y/December/18d .

See this SO answer for a deep-dive on the difference between month and months .

There are multiple ways to add the units years and months to a time_point . See this SO answer for a deep-dive on that topic.