How to convert DateTime object to json

Rather than using a wrapper, you can also create your own custom encoder passing the toEncodable argument.

import 'dart:convert' show JSON;

void main() {
  var dt = new DateTime.now();
  var str = JSON.encode(dt, toEncodable: myEncode);
  print(str);
}

dynamic myEncode(dynamic item) {
  if(item is DateTime) {
    return item.toIso8601String();
  }
  return item;
}