An application sends a ZGM_GETDOW message to get the day of the week of the julian date specified in wParam.
ZGM_GETDOW wParam = (WPARAM) (int) iJulianDate; //julian date lParam = 0; //not used; must be 0
If the julian date specified in wParam is valid, this message returns the day of the week of that date. Otherwise, the message returns -1.
The following values are returned based on the day of the week: