How to convert from UTC to local time in C?

Question

It\'s a simple question, but the solution appears to be far from simple. I would like to know how to convert from UTC to local time. I am looking for a solution in C that\'s

Answer 1

A simple and effective way: Add (or subtract) the number of seconds between your time zone and UTC (considering daylight saving time).

As an example that worked just fine a minute ago, on December 30, 2017, with U.S. Mountain Standard Time (no DST), which is 7 hours behind UTC:

time_t     current_time_UTC;
time_t     current_time_MST;

struct tm *current_broken_time_MST;

uint32_t seven_hours_in_seconds = 25200; // Get this any way you want

current_time_UTC = time (NULL);                                 // UTC
current_time_MST = current_time_UTC - seven_hours_in_seconds;   // MST

current_broken_time_MST = localtime (¤t_time_MST);        // MST

Enjoy.