calendar_entries.dart

final List<Map<String, List<String>>> entries = [
  {
    "2020-4-15": ["forex", "Movie"]
  },
  {"2020-4-22": []},
  {
    "2020-5-15": ["forex", "Movie"]
  },
  {
    "2020-6-14": ["forex", "forex", "Movie"]
  },
  {
    "2020-7-14": ["forex", "forex", "Movie"]
  },
  {
    "2020-8-13": ["forex", "forex", "Movie"]
  },
  {
    "2020-9-12": ["forex", "Movie", "Forex"]
  }
];

List<String> getEntries(DateTime dt) {
  String _date = "${dt.year}-${dt.month}-${dt.day}";
  print(_date);
  List<String> entry = [];

  for (int i = 0; i < entries.length; i++) {
    if (entries[i][_date] != null) {
      entry = entries[i][_date];
      break;
    }
  }

  return entry;
}

void main() {
  
  print(getEntries(DateTime(2020, 4, 10)));
  print("\n");
  print(getEntries(DateTime(2020, 4, 15)));
  print("\n");
  print(getEntries(DateTime(2020, 9, 12)));
  print("\n");
  print(getEntries(DateTime(2020, 7, 14)));

  
}