CODEWITHSUNDEEP
datetimedart
1DD
1DD

Reputation: 295

Dart - Two different dates produce identical difference inDays

I have been working on a flutter project and trying to filter results by a specific date when I notice the following behaviors.

main() {
  String v = '2020-08-03';
  int ms0 = 1596249000000;
  int ms1 = 1596368040000; // 
  int ms2 = 1596465736799;
  int ms3 = 1596472120778; //
  int ms4 = 1596623965588;
  
  print(DateTime.fromMillisecondsSinceEpoch(ms0));
  print(DateTime.fromMillisecondsSinceEpoch(ms1));
  print(DateTime.fromMillisecondsSinceEpoch(ms2));
  print(DateTime.fromMillisecondsSinceEpoch(ms3));
  print(DateTime.fromMillisecondsSinceEpoch(ms4));

 print(DateTime.parse(v).difference(DateTime.fromMillisecondsSinceEpoch(ms0)).inDays); 
 print(DateTime.parse(v).difference(DateTime.fromMillisecondsSinceEpoch(ms1)).inDays);
 print(DateTime.parse(v).difference(DateTime.fromMillisecondsSinceEpoch(ms2)).inDays);
 print(DateTime.parse(v).difference(DateTime.fromMillisecondsSinceEpoch(ms3)).inDays);
 print(DateTime.parse(v).difference(DateTime.fromMillisecondsSinceEpoch(ms4)).inDays);
}

Code above produces following results

2020-08-01 10:30:00.000
2020-08-02 19:34:00.000
2020-08-03 22:42:16.799
2020-08-04 00:28:40.778
2020-08-05 18:39:25.588
1
0
0
-1
-2

I don't understand how variables 'ms1' and 'ms2' would produce identical difference 'inDays'. Would somebody please help give some pointers? Thank you all.

Upvotes: 0

Views: 49

Answers (1)

Sergey Salnikov
Sergey Salnikov

Reputation: 1791

Day length is full 24 hour, full hour is 60 minutes

If difference is less than 24 hours by 1 second or 1 microsecond, etc - there is no full day counted

Going back to your example

2020-08-03 mean start of the day 00:00:00.000

and differs from

2020-08-02 19:34:00.000 only by 4h, 26m

2020-08-03 22:42:16.799 only by 22h, 42m, 16s, 799ms

This test explain

  test('datetime difference in days', () {
    final date = DateTime.parse('2020-08-03');
    final date1 = DateTime.fromMillisecondsSinceEpoch(1596368040000);
    final date2 = DateTime.fromMillisecondsSinceEpoch(1596465736799);

    print(date);  // 2020-08-03 00:00:00.000
    print(date1); // 2020-08-02 17:34:00.000
    print(date2); // 2020-08-03 20:42:16.799

    expect(date1.difference(date).inDays, equals(0));
    expect(date1.difference(date).inHours, equals(-6));

    expect(date2.difference(date).inDays, equals(0));
    expect(date2.difference(date).inHours, equals(20));
  });

Upvotes: 3

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