external(INT, "FileTimeToSystemTime", "FileTimeToSystemTime", "Kernel32.dll");
external(INT, "SystemTimeToFileTime", "SystemTimeToFileTime", "Kernel32.dll");

messagebox(dayofweek(15, 9, 2019)); // день, месяц, год


function dayofweek(int day, int month, int year)
{
char st[18], ft[8];
codhex(year, #st[0]); codhex(month, #st[2]); codhex(0, #st[4]); codhex(day, #st[6]);
codhex(0, #st[8]); codhex(0, #st[10]); codhex(0, #st[12]); codhex(0, #st[14]);
SystemTimeToFileTime(address(#st[0]), address(#ft[0]));
FileTimeToSystemTime(address(#ft[0]), address(#st[0]));
int R=codhexi(#st[4], 2);
if(R==0) return "воскресение";
if(R==1) return "понедельник";
if(R==2) return "вторник";
if(R==3) return "среда";
if(R==4) return "четверг";
if(R==5) return "пятница";
if(R==6) return "суббота";
}