[shagie]

That's a direct translation of struct_tm from time.h.

     External declarations, as well as the tm structure definition, are
     contained in the <time.h> include file.  The tm structure includes at
     least the following fields:

           int tm_sec;     /∗ seconds (0 - 60) ∗/
           int tm_min;     /∗ minutes (0 - 59) ∗/
           int tm_hour;    /∗ hours (0 - 23) ∗/
           int tm_mday;    /∗ day of month (1 - 31) ∗/
           int tm_mon;     /∗ month of year (0 - 11) ∗/
           int tm_year;    /∗ year - 1900 ∗/
           int tm_wday;    /∗ day of week (Sunday = 0) ∗/
           int tm_yday;    /∗ day of year (0 - 365) ∗/
           int tm_isdst;   /∗ is summer time in effect? ∗/
           char ∗tm_zone;  /∗ abbreviation of timezone name ∗/
           long tm_gmtoff; /∗ offset from UTC in seconds ∗/

You'll note that tm_year is years since 1900.

While working support at SGI in the late 90s, got a number of support tickets (there was a woman who worked for a government department (NASA?) who was very good at finding them in doing their y2k checks) about dates showing up as `20100`.