Does the mktime() library function adds an offset of 10 days to the output value?
I tried to implement a mktime() function myself, but noticed the lack of 10 days from the output value.
So, if I convert a (time_t) 1234567890 value to a (struct tm) and later converts it back (with my pseudo mktime() function) to a (time_t), the result is 1233703890 ( = 1234567890 - 10*24*60*60 )

Thank you.

 

This problem was caused by the leap years.
From 1970 until now, there were 10 leap years. The following PHP script shows that:

header('content-type: text/plain; charset=ASCII');
for($i=1970, $cnt=0; $i<2010; ++$i) {
    if ( !( !($i%4) && $i%100 || !($i%400) ) ) continue;
    echo $i, PHP_EOL;    ++$cnt;
}
echo PHP_EOL, 'Total leap years: ', $cnt;

Output:

1972
1976
1980
1984
1988
1992
1996
2000
2004
2008

Total leap years: 10