C code to get local time offset in minutes relative to UTC?

Question

I didn\'t find a trivial way to get the time offset in minutes between the local time and the UTC time.

At first I intended to use tzset() but it doesn\'t p

Answer 1

Does your system's strftime() function support the %z and %Z specifiers? On FreeBSD,

 %Z    is replaced by the time zone name.

 %z    is replaced by the time zone offset from UTC; a leading plus sign
       stands for east of UTC, a minus sign for west of UTC, hours and
       minutes follow with two digits each and no delimiter between them
       (common form for RFC 822 date headers).

and I can use this to print this:

$ date +"%Z: %z"
CEST: +0200

ISO C99 has this in 7.23.3.5 The strftime function:

%z     is replaced by the offset from UTC in the ISO 8601 format
       ‘‘−0430’’ (meaning 4 hours 30 minutes behind UTC, west of Greenwich),
       or by no characters if no time zone is determinable. [tm_isdst]
%Z     is replaced by the locale’s time zone name or abbreviation, or by no
       characters if no time zone is determinable. [tm_isdst]