type string datetime 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: Datetime to utc format

string foo = yourDateTime.ToUniversalTime()
                         .ToString("yyyy'-'MM'-'dd'T'HH':'mm':'ss'.'fff'Z'");