how to change string to date format code example

Example 1: convert string date to datetime and format

var dateString = "2020-09-25T10:13:21.246321+01:00";
String formattedDateString = DateFormat('do LLLL yyyy').format(DateTime.parse(dateString)); 
// formattedDateString - OUTPUT: "25 September 2020"

Example 2: how to convert string to datetime

import datetime
datetime.datetime.strptime(date_string, format)