How do I convert a date/time string to a DateTime object in Dart?

Say I have a string

"1974-03-20 00:00:00.000"

It is created using DateTime.now(), how do I convert the string back to a DateTime object?

DateTime has a parse method

var parsedDate = DateTime.parse('1974-03-20 00:00:00.000');

https://api.dartlang.org/stable/dart-core/DateTime/parse.html

There seem to be a lot of questions about parsing timestamp strings into DateTime. I will try to give a more general answer so that future questions can be directed here.

Your timestamp is in an ISO format. Examples: 1999-04-23, 1999-04-23 13:45:56Z, 19990423T134556.789. In this case, you can use DateTime.parse or DateTime.tryParse. (See the DateTime.parse documentation for the precise set of allowed inputs.)
Your timestamp is in a standard HTTP format. Examples: Fri, 23 Apr 1999 13:45:56 GMT, Friday, 23-Apr-99 13:45:56 GMT, Fri Apr 23 13:45:56 1999. In this case, you can use dart:io's HttpDate.parse function.
Your timestamp is in some local format. Examples: 23/4/1999, 4/23/99, April 23, 1999. You can use package:intl's DateFormat class and provide a pattern specifying how to parse the string:
```
import 'package:intl/intl.dart';

...

var dmyString = '23/4/1999';
var dateTime1 = DateFormat('d/M/yyyy').parse(dmyString);

var mdyString = '4/23/99'; 
var dateTime2 = DateFormat('M/d/yy').parse(mdyString);

var mdyFullString = 'April 23, 1999';
var dateTime3 = DateFormat('MMMM d, yyyy', 'en_US').parse(mdyFullString));
```
See the DateFormat documentation for more information about the pattern syntax.

DateFormat limitations:
- DateFormat cannot parse dates that lack explicit field separators. For such cases, you can resort to using regular expressions (see below).
- Prior to version 0.17.0 of package:intl, yy did not follow the -80/+20 rule that the documentation describes for inferring the century, so if you use a 2-digit year, you might need to adjust the century afterward.
- As of writing, DateFormat does not support time zones. If you need to deal with time zones, you will need to handle them separately.

Last resort: If your timestamps are in a fixed, known, numeric format, you always can use regular expressions to parse them manually:

var dmyString = '23/4/1999';

var re = RegExp(
  r'^'
  r'(?<day>[0-9]{1,2})'
  r'/'
  r'(?<month>[0-9]{1,2})'
  r'/'
  r'(?<year>[0-9]{4,})'
  r'$',
);

var match = re.firstMatch(dmyString);
if (match == null) {
  throw FormatException('Unrecognized date format');
}

var dateTime4 = DateTime(
  int.parse(match.namedGroup('year')!),
  int.parse(match.namedGroup('month')!),
  int.parse(match.namedGroup('day')!),
);

See https://stackoverflow.com/a/63402975/ for another example.

(I mention using regular expressions for completeness. There are many more points for failure with this approach, so I do not recommend it unless there's no other choice. DateFormat usually should be sufficient.)

How do I convert a date/time string to a DateTime object in Dart?

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