weekFromDateTime function
Implementation
int weekFromDateTime(DateTime date) {
int dayOfYear = int.parse(DateFormat("D").format(date));
int woy = ((dayOfYear - date.weekday + 10) / 7).floor();
if (woy < 1) {
woy = numOfWeeks(date.year - 1);
} else if (woy > numOfWeeks(date.year)) {
woy = 1;
}
return woy;
}