parsing - how do I parse an iso 8601 date (with optional milliseconds) to a struct tm in C++? -

i have string should specify date , time in iso 8601 format, may or may not have milliseconds in it, , wanting struct tm millisecond value may have been specified (which can assumed 0 if not present in string).

what involved in detecting whether string in correct format, converting user-specified string struct tm , millisecond values?

if weren't millisconds issue, use c function strptime(), not know defined behavior of function supposed when seconds contain decimal point.

as 1 final caveat, if @ possible, prefer solution not have dependency on functions found in boost (but i'm happy accept c++11 prerequisite).

the input going like:

2014-11-12t19:12:14.505z 

or

2014-11-12t12:12:14.505-5:00 

z, in case, indicates utc, time zone might used, , expressed + or - hours/minutes offset gmt. decimal portion of seconds field optional, fact may there @ why cannot use strptime() or std::get_time(), not describe particular defined behavior if such character found in seconds portion of string.

you can use c's sscanf (http://www.cplusplus.com/reference/cstdio/sscanf/) parse it:

const char *datestr = "2014-11-12t19:12:14.505z"; int y,m,d,h,m; float s; sscanf(datestr, "%d-%d-%dt%d:%d:%fz", &y, &m, &d, &h, &m, &s); 

if have std::string can called (http://www.cplusplus.com/reference/string/string/c_str/):

std::string datestr = "2014-11-12t19:12:14.505z"; sscanf(datestr.c_str(), "%d-%d-%dt%d:%d:%fz", &y, &m, &d, &h, &m, &s); 

if should handle different timezones need use sscanf return value - number of parsed arguments:

int tzh = 0, tzm = 0; if (6 < sscanf(datestr.c_str(), "%d-%d-%dt%d:%d:%f%d:%dz", &y, &m, &d, &h, &m, &s, &tzh, &tzm)) {     if (tzh < 0) {        tzm = -tzm;    // fix sign on minutes.     } } 

and can fill tm (http://www.cplusplus.com/reference/ctime/tm/) struct:

tm time; time.tm_year = y - 1900; // year since 1900 time.tm_mon = m - 1;     // 0-11 time.tm_mday = d;        // 1-31 time.tm_hour = h;        // 0-23 time.tm_min = m;         // 0-59 time.tm_sec = (int)s;    // 0-61 (0-60 in c++11) 

it can done std::get_time (http://en.cppreference.com/w/cpp/io/manip/get_time) since c++11 @barry mentioned in comment how parse iso 8601 date (with optional milliseconds) struct tm in c++?