code: function _getAge(Y) {
    switch (true) {
      case Y < 1700: return { m: 22, n: 2 };
      case Y < 1800: return { m: 23, n: 3 };
      case Y < 1900: return { m: 23, n: 4 };
      case Y < 2100: return { m: 24, n: 5 };
      case Y < 2200: return { m: 24, n: 6 };
      case Y < 2300: return { m: 25, n: 0 };
      case Y < 2400: return { m: 26, n: 1 };
      case Y < 2500: return { m: 25, n: 1 };
    }
  }
docs: https://en.wikipedia.org/wiki/Computus#Gauss's_Easter_algorithm