Problems with conversion between mktime and gmtime_r - c++

Question

If I define a broken-down time using struct tm, then convert it to time_t using mktime and the result try to get back again as an struct tm I thought I was going to get the same result.
OK, maybe the first time something change because I define tm_isdst = -1 so mktime maybe affect that value, but not the second time.
The following code does that:
void print(const tm& t)
{
std::cout << t.tm_mday << '/'
<< t.tm_mon << '/'
<< t.tm_year << ' '
<< t.tm_hour << ':'
<< t.tm_min << ':'
<< t.tm_sec << "; "
<< t.tm_wday << '|'
<< t.tm_isdst << '\n';
}
int main(){
tm t;
t.tm_sec = 32;
t.tm_min = 22;
t.tm_hour = 0;
t.tm_mday = 6;
t.tm_mon = 0;
t.tm_year = 2023 - 1900;
t.tm_wday = 5;
t.tm_isdst = -1;
print(t);
time_t timet0 = mktime(&t);
std::cout << "time_t0 = " << timet0 << '\n';
gmtime_r(&timet0, &t);
print(t);
time_t timet1 = mktime(&t);
std::cout << "time_t1 - time_t0 = " << (timet1 - timet0) << '\n';
std::cout << "time_t1 = " << timet1 << '\n';
gmtime_r(&timet1, &t);
print(t);
timet1 = mktime(&t);
std::cout << "time_t = " << timet1 << '\n';
gmtime_r(&timet1, &t);
print(t);
}
And the result of executing it is
6/0/123 0:22:32; 5|-1
time_t0 = 1672960952
5/0/123 23:22:32; 4|0
time_t1 - time_t0 = -3600
time_t1 = 1672957352
5/0/123 22:22:32; 4|0
time_t = 1672953752
5/0/123 21:22:32; 4|0
Why am I losing an hour every time I call the pair mktime/gmtime_r?