Better handling of time zones

We now send the current time zone to the server when serializing datetime objects.
This was causing entries to be saved some hours wrong or depending on the time, on
a different day.

Author: rolandgeider

lib/helpers/date.dart

@@ -0,0 +1,40 @@
+/*
+ * This file is part of wger Workout Manager <https://github.com/wger-project>.
+ * Copyright (C) wger Team
+ *
+ * wger Workout Manager is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * wger Workout Manager is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/// Returns a timezone aware DateTime object from a date and time string.
+DateTime getDateTimeFromDateAndTime(String date, String time) {
+  return DateTime.parse('$date $time');
+}
+
+/// Returns a list of [DateTime] objects from [first] to [last], inclusive.
+List<DateTime> daysInRange(DateTime first, DateTime last) {
+  final dayCount = last.difference(first).inDays + 1;
+  return List.generate(
+    dayCount,
+    (index) => DateTime.utc(first.year, first.month, first.day + index),
+  );
+}
+
+extension DateTimeExtension on DateTime {
+  bool isSameDayAs(DateTime other) {
+    final thisDay = DateTime(year, month, day);
+    final otherDay = DateTime(other.year, other.month, other.day);
+
+    return thisDay.isAtSameMomentAs(otherDay);
+  }
+}

lib/helpers/json.dart

@@ -53,6 +53,15 @@ String? dateToYYYYMMDD(DateTime? dateTime) {
   return DateFormat('yyyy-MM-dd').format(dateTime);
 }
 
+/// Convert a date to UTC and then to an ISO8601 string.
+///
+/// This makes sure that the serialized data has correct timezone information.
+/// Otherwise the django backend will possible treat the date as local time,
+/// which will not be correct in most cases.
+String dateToUtcIso8601(DateTime dateTime) {
+  return dateTime.toUtc().toIso8601String();
+}
+
 /*
  * Converts a time to a date object.
  * Needed e.g. when the wger api only sends a time but no date information.

lib/helpers/misc.dart

@@ -63,38 +63,6 @@ String repText(
   return out.join(' ');
 }
 
-/// Returns a list of [DateTime] objects from [first] to [last], inclusive.
-List<DateTime> daysInRange(DateTime first, DateTime last) {
-  final dayCount = last.difference(first).inDays + 1;
-  return List.generate(
-    dayCount,
-    (index) => DateTime.utc(first.year, first.month, first.day + index),
-  );
-}
-
-extension TimeOfDayExtension on TimeOfDay {
-  bool isAfter(TimeOfDay other) {
-    return toMinutes() > other.toMinutes();
-  }
-
-  bool isBefore(TimeOfDay other) {
-    return toMinutes() < other.toMinutes();
-  }
-
-  int toMinutes() {
-    return (hour * 60) + minute;
-  }
-}
-
-extension DateTimeExtension on DateTime {
-  bool isSameDayAs(DateTime other) {
-    final thisDay = DateTime(year, month, day);
-    final otherDay = DateTime(other.year, other.month, other.day);
-
-    return thisDay.isAtSameMomentAs(otherDay);
-  }
-}
-
 void launchURL(String url, BuildContext context) async {
   final scaffoldMessenger = ScaffoldMessenger.of(context);
   final launched = await launchUrl(Uri.parse(url));

lib/models/nutrition/log.dart

@@ -36,7 +36,7 @@ class Log {
   @JsonKey(required: true, name: 'plan')
   int planId;
 
-  @JsonKey(required: true)
+  @JsonKey(required: true, toJson: dateToUtcIso8601)
   late DateTime datetime;
 
   String? comment;

lib/models/nutrition/log.g.dart

@@ -19,8 +19,8 @@
 import 'package:flutter/material.dart';
 import 'package:json_annotation/json_annotation.dart';
 import 'package:wger/helpers/consts.dart';
+import 'package:wger/helpers/date.dart';
 import 'package:wger/helpers/json.dart';
-import 'package:wger/helpers/misc.dart';
 import 'package:wger/models/nutrition/log.dart';
 import 'package:wger/models/nutrition/meal_item.dart';
 import 'package:wger/models/nutrition/nutritional_values.dart';

lib/models/nutrition/meal.dart

@@ -38,7 +38,7 @@ class NutritionalPlan {
   @JsonKey(required: true)
   late String description;
 
-  @JsonKey(required: true, name: 'creation_date', toJson: dateToYYYYMMDD)
+  @JsonKey(required: true, name: 'creation_date', toJson: dateToUtcIso8601)
   late DateTime creationDate;
 
   @JsonKey(required: true, name: 'only_logging')

lib/models/nutrition/nutritional_plan.dart

@@ -80,7 +80,7 @@ class Log {
   @JsonKey(includeFromJson: false, includeToJson: false)
   late WeightUnit? weightUnitObj;
 
-  @JsonKey(required: true, toJson: dateToYYYYMMDD)
+  @JsonKey(required: true, toJson: dateToUtcIso8601)
   late DateTime date;
 
   Log({