C++ mktime returning random dates

Question

I\'m trying to convert a date string to a time_t, but mktime() is returning seemingly random dates:

string datetime = \"2014-12-10 10:30\";
stru         


        

Answer 1

You need to properly zero-initialize all of the other fields of the struct tm instance before calling strptime(), since it doesn't necessarily initialize every field. From the strptime() POSIX specification:

It is unspecified whether multiple calls to strptime() using the same tm structure will update the current contents of the structure or overwrite all contents of the structure. Conforming applications should make a single call to strptime() with a format and all data needed to completely specify the date and time being converted.

For example, this should suffice:

struct tm tmInfo = {0};

Answer 2

The below code would do the work, if you want current system time in an format

 time_t current_time;
 struct tm *loctime;

 memset(buffer,0,strlen(buffer));
 current_time = time(NULL);
 loctime = localtime(&current_time);
 strftime(buffer,250,"--> %d/%m/%y  %H:%M:%S",loctime);

Answer 3

You have to initialize the struct to 0 beforehand or also input the seconds:

string datetime = "2014-12-10 10:30";
struct tm tmInfo = { 0 };
strptime(datetime.c_str(), "%Y-%m-%d %H:%M", &tmInfo);

or

string datetime = "2014-12-10 10:30:00";
struct tm tmInfo;
strptime(datetime.c_str(), "%Y-%m-%d %H:%M:%S", &tmInfo);