next-year
The "next-year" signal is emitted when the user either clicks on the year arrow forward, or when the user selects a greyed-out day from the following January when December is currently displayed. It cannot be emitted through the program itself; use "month-changed" if you need to do this.
Callback function
void callback(GtkCalendar calendar);
忘却曲線を使ってこの知識を確実に記憶に残す
