So i am getting my time from an api that returns epoch time and i need to pass that time into a Real Time Clock function which accepts this dateTime structure

datetime_t t = {         // Friday June 5,  Hour 15, Minute 45, Sec 00
        .year  = 2020,
        .month = 06,
        .day   = 05,
        .dotw  = 5, // 0 is Sunday, so 5 is Friday
        .hour  = 15,
        .min   = 45,
        .sec   = 00
};

I need help creating a formula to get those individual values. I think i have made a formula for the easy ones.

sec  = epochTime%60
min  = floor((epochTime%3600)/60)
hour = floor((epochTime%86400)/3600)

as for the others it is not that easy anymore as there are leap years and such. i have to do this with only standard libraries or you can suggest a web api that returns me those value (it has to be only 1 api for all of those data)

CodePudding user response：

Assuming the epoch time is the UNIX epoch, i.e. seconds since 1970/01/01 00:00:00 UTC, you can use the localtime function. This function takes the address of a time_t containing epoch time and splits it into its component values, assuming the local timezone:

struct tm *tm;
time_t t = time(NULL);
tm = localtime(&t);

The returned structure is defined as follows:

       struct tm {
           int tm_sec;         /* seconds */
           int tm_min;         /* minutes */
           int tm_hour;        /* hours */
           int tm_mday;        /* day of the month */
           int tm_mon;         /* month */
           int tm_year;        /* year */
           int tm_wday;        /* day of the week */
           int tm_yday;        /* day in the year */
           int tm_isdst;       /* daylight saving time */
       };

Where tm_year is years since 1900, tm_mon is in the range 0-11, and tm_wday is in the range 0-6 (Sun-Sat).

If you want UTC time, you can use gmtime instead with the same parameters / return type.