Fix daylight-saving issue

CHANGELOG.md

@@ -1,3 +1,7 @@
+## 1.1.1
+
+* Fix daylight-saving issue
+
 ## 1.1.0
 
 * Stable null safety release

README.md

@@ -1,11 +1,10 @@
 # isoweek
 
-A lightweight Dart package which provides the class Week (based on the ISO 8601 format). Instances represent specific weeks spanning Monday to Sunday. 
+A lightweight Dart package which provides the class Week (based on the local time). Instances represent specific weeks spanning Monday to Sunday. 
 An ISO week-numbering year has 52 or 53 full weeks. Week 1 is defined to be the first week with 4 or more days in January.
 
-See also: https://en.wikipedia.org/wiki/ISO_week_date
-
-(This package is inspired by the isoweek Python package: https://pypi.org/project/isoweek/)
+It’s called isoweek because this is the week definition of [ISO 8601](https://en.wikipedia.org/wiki/ISO_week_date).
+This package is inspired by the [isoweek Python package](https://pypi.org/project/isoweek/).
 
 ### Example
 
@@ -14,12 +13,15 @@ import 'package:isoweek/isoweek.dart';
 
 void main() {
   Week currentWeek = Week.current();
-  print(currentWeek);
+  print('Current week: $currentWeek');
   //OUTPUT: 2021W13
 
+  print('Days of current week: ${currentWeek.days}');
+  //OUTPUT: [2021-03-29 00:00:00.000, 2021-03-30 00:00:00.000, ...]
+
   Week nextWeek = currentWeek.next;
   print('Days of next week: ${nextWeek.days}');
-  //OUTPUT: Days of next week: [2021-04-05 01:00:00.000, 2021-04-06 01:00:00.000, ...]
+  //OUTPUT: Days of next week: [2021-04-05 00:00:00.000, 2021-04-06 00:00:00.000, ...]
 
   Week previousWeek = currentWeek.previous;
   print('Days of previous week: ${previousWeek.days}');
@@ -29,19 +31,17 @@ void main() {
   print('5 weeks ahead: $futureWeek');
   //OUTPUT: 5 weeks ahead: 2021W18
 
-  DateTime myBirthday = DateTime.utc(2020, 11, 16);
-  Week birthdayWeek = Week.fromDate(myBirthday);
+  Week birthdayWeek = Week.fromDate(DateTime(2020, 11, 16));
   print(
       'The week number of my birthday in 2020 was ${birthdayWeek.weekNumber}');
   //OUTPUT: The week number of my birthday in 2020 was 47
 
-  String isoWeek = '2021W25';
-  Week weekFromIso = Week.fromIsoString(isoWeek);
-  print('Week from ISO: $weekFromIso');
+  Week weekFromIso = Week.fromISOString('2021W25');
+  print('Week from ISO string: $weekFromIso');
   //OUTPUT: Week from ISO: 2021W25
 
   DateTime firstDay = weekFromIso.day(0);
   print('The Week $weekFromIso starts with $firstDay');
-  //OUTPUT: The Week 2021W25 starts with 2021-06-21 01:00:00.000
+  //OUTPUT: The Week 2021W25 starts with 2021-06-21 00:00:00.000
 }
 ```

example/example.dart

@@ -2,12 +2,15 @@ import 'package:isoweek/isoweek.dart';
 
 void main() {
   Week currentWeek = Week.current();
-  print(currentWeek);
+  print('Current week: $currentWeek');
   //OUTPUT: 2021W13
 
+  print('Days of current week: ${currentWeek.days}');
+  //OUTPUT: [2021-03-29 00:00:00.000, 2021-03-30 00:00:00.000, ...]
+
   Week nextWeek = currentWeek.next;
   print('Days of next week: ${nextWeek.days}');
-  //OUTPUT: Days of next week: [2021-04-05 01:00:00.000, 2021-04-06 01:00:00.000, ...]
+  //OUTPUT: Days of next week: [2021-04-05 00:00:00.000, 2021-04-06 00:00:00.000, ...]
 
   Week previousWeek = currentWeek.previous;
   print('Days of previous week: ${previousWeek.days}');
@@ -17,18 +20,16 @@ void main() {
   print('5 weeks ahead: $futureWeek');
   //OUTPUT: 5 weeks ahead: 2021W18
 
-  DateTime myBirthday = DateTime.utc(2020, 11, 16);
-  Week birthdayWeek = Week.fromDate(myBirthday);
+  Week birthdayWeek = Week.fromDate(DateTime(2020, 11, 16));
   print(
       'The week number of my birthday in 2020 was ${birthdayWeek.weekNumber}');
   //OUTPUT: The week number of my birthday in 2020 was 47
 
-  String isoWeek = '2021W25';
-  Week weekFromIso = Week.fromISOString(isoWeek);
-  print('Week from ISO: $weekFromIso');
+  Week weekFromIso = Week.fromISOString('2021W25');
+  print('Week from ISO string: $weekFromIso');
   //OUTPUT: Week from ISO: 2021W25
 
   DateTime firstDay = weekFromIso.day(0);
   print('The Week $weekFromIso starts with $firstDay');
-  //OUTPUT: The Week 2021W25 starts with 2021-06-21 01:00:00.000
+  //OUTPUT: The Week 2021W25 starts with 2021-06-21 00:00:00.000
 }

lib/isoweek.dart

@@ -71,19 +71,20 @@ class Week extends Equatable {
 
   /// Return the week that many number of weeks into the future.
   Week addWeeks(int weeks) {
-    return Week.fromDate(day(0).add(Duration(days: 7 * weeks)));
+    return Week.fromDate(day(0).addWeeks(weeks));
   }
 
   /// Return the week that many number of weeks in the past.
   Week subtractWeeks(int weeks) {
-    return Week.fromDate(day(0).subtract(Duration(days: 7 * weeks)));
+    return Week.fromDate(day(0).subtractWeeks(weeks));
   }
 
   /// Return a day of the week as a DateTime object based on the provided day index. Day 0 is Monday.
   DateTime day(int day) {
     // According to ISO the Jan 4th must be in week 1
-    final d = DateTime(year, 1, 4);
-    return d.add(Duration(days: (weekNumber - 1) * 7 + (-d.weekday + day) + 1));
+    final addDays =
+        (weekNumber - 1) * 7 + (-DateTime(year, 1, 4).weekday + day) + 1;
+    return DateTime(year, 1, 4).addDays(addDays);
   }
 
   /// Return the next week.
@@ -93,16 +94,45 @@ class Week extends Equatable {
   Week get previous => subtractWeeks(1);
 
   /// Return a list of all days in the week.
-  List<DateTime> get days {
-    final monday = day(0);
-    final days = <DateTime>[];
-    for (var i in [0, 1, 2, 3, 4, 5, 6]) {
-      days.add(monday.add(Duration(days: i)));
-    }
-    return days;
-  }
+  List<DateTime> get days => List.generate(7, (i) => day(0).addDays(i));
 
   /// Return an ISO formatted string like "2020W01".
   @override
   String toString() => '${year}W${weekNumber.toString().padLeft(2, '0')}';
 }
+
+extension DateTimeUtils on DateTime {
+  /// Alternative to add(days: x) because of daylight-saving issues.
+  DateTime addDays(int days) => copyWith(day: day + days);
+
+  /// Alternative to add(days: x * 7) because of daylight-saving issues.
+  DateTime addWeeks(int weeks) => copyWith(day: day + weeks * 7);
+
+  /// Alternative to subtract(days: 7) because of daylight-saving issues.
+  DateTime subtractDays(int days) => copyWith(day: day - days);
+
+  /// Alternative to subtract(days: x * 7) because of daylight-saving issues.
+  DateTime subtractWeeks(int weeks) => copyWith(day: day - weeks * 7);
+
+  DateTime copyWith({
+    int? year,
+    int? month,
+    int? day,
+    int? hour,
+    int? minute,
+    int? second,
+    int? millisecond,
+    int? microsecond,
+  }) {
+    return DateTime(
+      year ?? this.year,
+      month ?? this.month,
+      day ?? this.day,
+      hour ?? this.hour,
+      minute ?? this.minute,
+      second ?? this.second,
+      millisecond ?? this.millisecond,
+      microsecond ?? this.microsecond,
+    );
+  }
+}

pubspec.yaml

@@ -1,6 +1,6 @@
 name: isoweek
 description: A lightweight Dart package which provides the class Week (based on the ISO 8601 format).
-version: 1.1.0
+version: 1.1.1
 homepage: https://jensbecker.dev
 repository: https://github.com/devj3ns/isoweek
 issue_tracker: https://github.com/devj3ns/isoweek/issues

test/isoweek_test.dart

@@ -55,4 +55,14 @@ void main() {
       expect(monday, equals(monday2));
     },
   );
+
+  test(
+    'Test if all DateTimes in the days getter have a time of 00:00:00.',
+    () {
+      final daysWithTimeEqualToZero = Week.current().days.where(
+          (date) => date.hour == 0 && date.minute == 0 && date.second == 0);
+
+      expect(daysWithTimeEqualToZero.length, equals(7));
+    },
+  );
 }