gcal-application.c: Fix tm -> GDateTime year conversion.
g_date_time_new() expects an actual year, while the tm struct only provides the number of years since 1900.
ref: https://pubs.opengroup.org/onlinepubs/7908799/xsh/time.h.html
g_date_time_new() expects an actual year, while the tm struct only provides the number of years since 1900.
ref: https://pubs.opengroup.org/onlinepubs/7908799/xsh/time.h.html