An application sends a ZGM_GETREGDATEYEAR message to get the year of the date in the internal date register.
ZGM_GETREGDATEYEAR
wParam = 0; //not used; must be 0
lParam = 0; //not used; must be 0
If the date in the internal date register is valid, this message returns the year of that date. Otherwise, the message returns 0.