calculateDueDate method
Implementation
static DateTime calculateDueDate(CardState state) {
DateTime result = state.lastReviewed;
var newHour = 3;
var newDay = result.day + state.interval.ceil();
DateTime newResult = result.toLocal();
newResult = DateTime(result.year, result.month, newDay, newHour,
result.minute, result.second, result.millisecond, result.microsecond);
return newResult;
}