Exiv2

Recently I've observed a problem with exiv2 '-T' option in case of
daylight saving time. I'm using it for couple of years but saw this just
now. When time in exif data is read, one hour is added to the time when
daylight saving time is in effect.

The logic is in src/actions.cpp:

'int str2Tm(const std::string& timeStr, struct tm* tm)' converts the string
of the date to broken down struct tm. It is then converted to time_t with
timegm(struct tm tm). The resulted time_t variable is checked with -1 and
converted back to struct tm with gmtime_r or std::gmtime(time_t *t),
tm_isdst is modified by gmtime variant and set from -1 to 0 (no dst for GMT).
'int Timestamp::read(struct tm tm)' is called from ::run() to convert
struct tm to time_t value using mktime, which normalizes it. When the time
zone is with daylight saving time in effect it will set tm_isdst to 1.
Additionally it will increment tm_hour with 1, which is the reason for the
observed difference with 1 hour.

As I see there are two ways to fix this problem:

1) in 'int str2Tm(const std::string& timeStr, struct tm* tm)' - add
temporary struct tm variable and execute localtime to get the correct
tm_isdst flag, copy tm_isdt to the original tm, decrement tm_hour if
tm_isdst is set to compensate later conversion with mktime. If tm_hour is
0 make it 23, and so on for tm_mday and the other affected struct tm
members.

2) In 'int Timestamp::read(struct tm* tm)' - add check if tm_isdst=1 to
substract 3600 seconds from 't' to compensate mktime.

Variant 1) is better if there are many callers which use mktime or similar
timezone dependent function.
Variant 2) is a lot simpler and enough for this particular option of exiv2.

--- exiv2-0.21.1/src/actions.cpp 2011-02-13 16:39:15.000000000 0200
++ exiv2-0.21.1/src/actions.cpp 2011-04-24 02:33:16.199983003 0300
@ -1742,6 +1742,8 @ namespace {
time_t t = mktime(tm);
if (t != (time_t)-1) {
rc = 0;
if (tm->tm_isdst && t >= 3600)
+ t -= 3600;
actime_ = t;
modtime_ = t;
}

Regards,
Boyan