Flutter: Find the number of days between two dates

Question

I currently have a user's profile page that brings out their date of birth and other details. But I am planning to find the days before their birthday by calculating the difference between today's date and the date of birth obtained from the user.

User's Date of Birth

And this is today's date obtained by using the intl package.

Today's date

I/flutter ( 5557): 09-10-2018 

The problem I am facing now is, How do I calculate the difference in days of these two dates?

Are there any specific formulas or packages that are available for me to check out?

Answer 1

You can use the difference method provide by DateTime class

 //the birthday's date  final birthday = DateTime(1967, 10, 12);  final date2 = DateTime.now();  final difference = date2.difference(birthday).inDays; 

UPDATE

Since many of you reported there is a bug with this solution and to avoid more mistakes, I'll add here the correct solution made by @MarcG, all the credits to him.

  int daysBetween(DateTime from, DateTime to) {      from = DateTime(from.year, from.month, from.day);      to = DateTime(to.year, to.month, to.day);    return (to.difference(from).inHours / 24).round();   }     //the birthday's date    final birthday = DateTime(1967, 10, 12);    final date2 = DateTime.now();    final difference = daysBetween(birthday, date2); 

This is the original answer with full explanation: https://stackoverflow.com/a/67679455/666221

Answer 2

The accepted answer is wrong. Don't use it.

This is correct:

int daysBetween(DateTime from, DateTime to) {   from = DateTime(from.year, from.month, from.day);   to = DateTime(to.year, to.month, to.day);   return (to.difference(from).inHours / 24).round(); } 

Testing:

DateTime date1 = DateTime.parse("2020-01-09 23:00:00.299871"); DateTime date2 = DateTime.parse("2020-01-10 00:00:00.299871");  expect(daysBetween(date1, date2), 1); // Works! 

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Explanation why the accepted answer is wrong:

Just run this:

int daysBetween_wrong1(DateTime date1, DateTime date2) {   return date1.difference(date2).inDays; }  DateTime date1 = DateTime.parse("2020-01-09 23:00:00.299871"); DateTime date2 = DateTime.parse("2020-01-10 00:00:00.299871");  // Should return 1, but returns 0. expect(daysBetween_wrong1(date1, date2), 0); 

Note: Because of daylight savings, you can have a 23 hours difference between some day and the next day, even if you normalize to 0:00. That's why the following is ALSO incorrect:

// Fails, for example, when date2 was moved 1 hour before because of daylight savings. int daysBetween_wrong2(DateTime date1, DateTime date2) {   from = DateTime(date1.year, date1.month, date1.day);     to = DateTime(date2.year, date2.month, date2.day);   return date2.difference(date1).inDays;  } 

Rant: If you ask me, Dart DateTime is very bad. It should at least have basic stuff like daysBetween and also timezone treatment etc.

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Update: The package https://pub.dev/packages/time_machine claims to be a port of Noda Time. If that's the case, and it's ported correctly (I haven't tested it yet) then that's the Date/Time package you should probably use.