toString method
Returns a human-readable string for this instance.
The resulting string can be parsed back using parse.
Implementation
String toString() {
String y = _fourDigits(year);
String m = _twoDigits(month);
String d = _twoDigits(day);
String h = _twoDigits(hour);
String min = _twoDigits(minute);
String sec = _twoDigits(second);
String ms = _threeDigits(millisecond);
return "$y-$m-$d $h:$min:$sec.$ms";
}