How to convert date and time to timestamp?

[IlyaM]

Hi, I use IoT sdk with my iPhone to get current date and time, date comes in ble_cts_c_evt_t structure, how can I convert it to timestamp, I know that I have to subscribe Jan 1, 1970 from current date and multiple all by 84600, but maybe is there more trivial way?

[Bastien Reynard]

You could use the mktime() function from the ANSI C library. See this example.

[IlyaM]

If I use mktime, I get incorrect data

struct tm time_struct;
ble_date_time_t datetime = p_evt->params.current_time.exact_time_256.day_date_time.date_time;
time_t newtime;
time_struct.tm_year = datetime.year - 1900;
time_struct.tm_mon = datetime.month;
time_struct.tm_mday = datetime.day;
time_struct.tm_hour = datetime.hours;
time_struct.tm_min = datetime.minutes;
time_struct.tm_sec = datetime.seconds;
newtime = mktime(&time_struct);

NRF_LOG_INFO("Timestamp is %ld\r\n", newtime); // got tomorrow day

[Bjørn Kvaale]

This devzone case might be helpful. In addition, the current time application in the nrf sdk could be helpful. See the current_time_print() function in the main.c file for more info. The current_time_print() function also takes in a ble_cts_c_evt_t struct & converts the data to hours, minutes, seconds & fractions of a second.

[IlyaM]

My app based on this current time application, and I got the correct date and time, but when I put it in tm structure and called mktime, I got wrong value of timestamp. Usually one month forward, i.e. if today is 19.03.2018 10:56:34, then my timestamp (after converting back in online service) shows 19.04.2018 10:56:34 (or UTC0 7:56:34)

[Bjørn Kvaale]

Is the time always one month forward? If so, it seems like there is some kind of offset that leads to an incorrect date.