qemu_timedate_diff() shouldn't modify its argument. The caller of qemu_timedate_diff() does not expect that tm it passes to the function will be modified, but mktime() is destructive and modifies its argument. Pass a copy of tm to it and set tm_isdst so that mktime() will not rely on it since its value may be outdated. Signed-off-by: Gleb Natapov <gleb@redhat.com> Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>