C++11 number of days since date

Question

I need to store date in flat file. Is there any simple metod to get number of days since particular date (for example since 1 AD) using standard libary in C++11? The only one I know is to:

• obtain std::tm structure, set all time values to 0
• convert it to std::time_t (I do not know proper method yet)
• divide time_t to get the resolution of one day

Can I perform it easier?

Answer 1

What you said sounds reasonable to start with. You can convert the struct tm to time_t using mktime. Note that mktime interprets its input as local time according to the system/environment settings, and there is no UTC counterpart that's as widely available without relying on "extra" libraries, but maybe that's not a problem for you.