I want to convert UTC timestamp in epoch time seconds considering DST in C language. I am doing development on VS 2005 as this is legacy product. I gone through various websites but it is not useful.
We can do this by boost library but it is not recommended.
I am passing input as "2017-03-12T01:00:00Z" i.e. UTC timestamp, and I want epoch time of it i.e. in seconds. When I convert this epoch time back to UTC time, it should give me exact result as input timestamp.
You can make use of mktime().
According to the man page, you have to parse the input and fill up the structure tm, defined as
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 */
};
and then, make a call to mktime() as
time_t result;
result = mktime(&t);
Point to note: Please read the linked manual and check for the applicable values of the structure members, especially
tm_monThe number of months since January, in the range 0 to 11.
and
tm_yearThe number of years since 1900.
