The month argument for g_date_time_new() is 1-based, while the tm struct is 0-based. Follow-up to: a0aa36b6d2 ref: https://pubs.opengroup.org/onlinepubs/7908799/xsh/time.h.html
a0aa36b6d2
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