__tm_gmtoff
val = __tm_to_secs(tm) - tm->__tm_gmtoff;
tm->__tm_gmtoff/3600*100 + tm->__tm_gmtoff%3600/60);
tm->__tm_gmtoff = (s[1]-'0')*36000+(s[2]-'0')*3600
if (neg) tm->__tm_gmtoff = -tm->__tm_gmtoff;
tm->__tm_gmtoff = 0;
__secs_to_zone(t, 1, &new.tm_isdst, &new.__tm_gmtoff, &opp, &new.__tm_zone);
t -= opp - new.__tm_gmtoff;
t -= new.__tm_gmtoff;
__secs_to_zone(t, 0, &new.tm_isdst, &new.__tm_gmtoff, &opp, &new.__tm_zone);
if (__secs_to_tm(t + new.__tm_gmtoff, &new) < 0) goto error;
tm->__tm_gmtoff = 0;