diff --git a/backend-dart/lib/application/service/dto/project_dto.dart b/backend-dart/lib/application/service/dto/project_dto.dart
index d155475..6b0bbdf 100644
--- a/backend-dart/lib/application/service/dto/project_dto.dart
+++ b/backend-dart/lib/application/service/dto/project_dto.dart
@@ -37,7 +37,6 @@ class ProjectCreateDto with _$ProjectCreateDto {
 @freezed
 class ProjectUpdateDto with _$ProjectUpdateDto {
   const factory ProjectUpdateDto({
-    required String id,
     String? name,
     String? description,
     String? clientId,
diff --git a/backend-dart/lib/application/service/dto/project_dto.freezed.dart b/backend-dart/lib/application/service/dto/project_dto.freezed.dart
index 55d5cde..f8340d2 100644
--- a/backend-dart/lib/application/service/dto/project_dto.freezed.dart
+++ b/backend-dart/lib/application/service/dto/project_dto.freezed.dart
@@ -509,7 +509,6 @@ ProjectUpdateDto _$ProjectUpdateDtoFromJson(Map<String, dynamic> json) {
 
 /// @nodoc
 mixin _$ProjectUpdateDto {
-  String get id => throw _privateConstructorUsedError;
   String? get name => throw _privateConstructorUsedError;
   String? get description => throw _privateConstructorUsedError;
   String? get clientId => throw _privateConstructorUsedError;
@@ -532,11 +531,7 @@ abstract class $ProjectUpdateDtoCopyWith<$Res> {
       _$ProjectUpdateDtoCopyWithImpl<$Res, ProjectUpdateDto>;
   @useResult
   $Res call(
-      {String id,
-      String? name,
-      String? description,
-      String? clientId,
-      String? userId});
+      {String? name, String? description, String? clientId, String? userId});
 }
 
 /// @nodoc
@@ -554,17 +549,12 @@ class _$ProjectUpdateDtoCopyWithImpl<$Res, $Val extends ProjectUpdateDto>
   @pragma('vm:prefer-inline')
   @override
   $Res call({
-    Object? id = null,
     Object? name = freezed,
     Object? description = freezed,
     Object? clientId = freezed,
     Object? userId = freezed,
   }) {
     return _then(_value.copyWith(
-      id: null == id
-          ? _value.id
-          : id // ignore: cast_nullable_to_non_nullable
-              as String,
       name: freezed == name
           ? _value.name
           : name // ignore: cast_nullable_to_non_nullable
@@ -594,11 +584,7 @@ abstract class _$$ProjectUpdateDtoImplCopyWith<$Res>
   @override
   @useResult
   $Res call(
-      {String id,
-      String? name,
-      String? description,
-      String? clientId,
-      String? userId});
+      {String? name, String? description, String? clientId, String? userId});
 }
 
 /// @nodoc
@@ -614,17 +600,12 @@ class __$$ProjectUpdateDtoImplCopyWithImpl<$Res>
   @pragma('vm:prefer-inline')
   @override
   $Res call({
-    Object? id = null,
     Object? name = freezed,
     Object? description = freezed,
     Object? clientId = freezed,
     Object? userId = freezed,
   }) {
     return _then(_$ProjectUpdateDtoImpl(
-      id: null == id
-          ? _value.id
-          : id // ignore: cast_nullable_to_non_nullable
-              as String,
       name: freezed == name
           ? _value.name
           : name // ignore: cast_nullable_to_non_nullable
@@ -649,17 +630,11 @@ class __$$ProjectUpdateDtoImplCopyWithImpl<$Res>
 @JsonSerializable()
 class _$ProjectUpdateDtoImpl implements _ProjectUpdateDto {
   const _$ProjectUpdateDtoImpl(
-      {required this.id,
-      this.name,
-      this.description,
-      this.clientId,
-      this.userId});
+      {this.name, this.description, this.clientId, this.userId});
 
   factory _$ProjectUpdateDtoImpl.fromJson(Map<String, dynamic> json) =>
       _$$ProjectUpdateDtoImplFromJson(json);
 
-  @override
-  final String id;
   @override
   final String? name;
   @override
@@ -671,7 +646,7 @@ class _$ProjectUpdateDtoImpl implements _ProjectUpdateDto {
 
   @override
   String toString() {
-    return 'ProjectUpdateDto(id: $id, name: $name, description: $description, clientId: $clientId, userId: $userId)';
+    return 'ProjectUpdateDto(name: $name, description: $description, clientId: $clientId, userId: $userId)';
   }
 
   @override
@@ -679,7 +654,6 @@ class _$ProjectUpdateDtoImpl implements _ProjectUpdateDto {
     return identical(this, other) ||
         (other.runtimeType == runtimeType &&
             other is _$ProjectUpdateDtoImpl &&
-            (identical(other.id, id) || other.id == id) &&
             (identical(other.name, name) || other.name == name) &&
             (identical(other.description, description) ||
                 other.description == description) &&
@@ -691,7 +665,7 @@ class _$ProjectUpdateDtoImpl implements _ProjectUpdateDto {
   @JsonKey(includeFromJson: false, includeToJson: false)
   @override
   int get hashCode =>
-      Object.hash(runtimeType, id, name, description, clientId, userId);
+      Object.hash(runtimeType, name, description, clientId, userId);
 
   /// Create a copy of ProjectUpdateDto
   /// with the given fields replaced by the non-null parameter values.
@@ -712,8 +686,7 @@ class _$ProjectUpdateDtoImpl implements _ProjectUpdateDto {
 
 abstract class _ProjectUpdateDto implements ProjectUpdateDto {
   const factory _ProjectUpdateDto(
-      {required final String id,
-      final String? name,
+      {final String? name,
       final String? description,
       final String? clientId,
       final String? userId}) = _$ProjectUpdateDtoImpl;
@@ -721,8 +694,6 @@ abstract class _ProjectUpdateDto implements ProjectUpdateDto {
   factory _ProjectUpdateDto.fromJson(Map<String, dynamic> json) =
       _$ProjectUpdateDtoImpl.fromJson;
 
-  @override
-  String get id;
   @override
   String? get name;
   @override
diff --git a/backend-dart/lib/application/service/dto/project_dto.g.dart b/backend-dart/lib/application/service/dto/project_dto.g.dart
index 98b1d01..1c24ab0 100644
--- a/backend-dart/lib/application/service/dto/project_dto.g.dart
+++ b/backend-dart/lib/application/service/dto/project_dto.g.dart
@@ -49,7 +49,6 @@ Map<String, dynamic> _$$ProjectCreateDtoImplToJson(
 _$ProjectUpdateDtoImpl _$$ProjectUpdateDtoImplFromJson(
         Map<String, dynamic> json) =>
     _$ProjectUpdateDtoImpl(
-      id: json['id'] as String,
       name: json['name'] as String?,
       description: json['description'] as String?,
       clientId: json['clientId'] as String?,
@@ -59,7 +58,6 @@ _$ProjectUpdateDtoImpl _$$ProjectUpdateDtoImplFromJson(
 Map<String, dynamic> _$$ProjectUpdateDtoImplToJson(
         _$ProjectUpdateDtoImpl instance) =>
     <String, dynamic>{
-      'id': instance.id,
       'name': instance.name,
       'description': instance.description,
       'clientId': instance.clientId,
diff --git a/backend-dart/lib/application/service/dto/time_entry_dto.dart b/backend-dart/lib/application/service/dto/time_entry_dto.dart
index c5d6975..963355d 100644
--- a/backend-dart/lib/application/service/dto/time_entry_dto.dart
+++ b/backend-dart/lib/application/service/dto/time_entry_dto.dart
@@ -8,7 +8,7 @@ class TimeEntryDto with _$TimeEntryDto {
   const factory TimeEntryDto({
     required String id,
     required DateTime startTime,
-    required DateTime endTime,
+    required DateTime? endTime,
     String? description,
     required String userId,
     required String projectId,
@@ -25,7 +25,7 @@ class TimeEntryDto with _$TimeEntryDto {
 class TimeEntryCreateDto with _$TimeEntryCreateDto {
   const factory TimeEntryCreateDto({
     required DateTime startTime,
-    required DateTime endTime,
+    DateTime? endTime,
     String? description,
     required String userId,
     required String projectId,
diff --git a/backend-dart/lib/application/service/dto/time_entry_dto.freezed.dart b/backend-dart/lib/application/service/dto/time_entry_dto.freezed.dart
index 9e04412..3daae46 100644
--- a/backend-dart/lib/application/service/dto/time_entry_dto.freezed.dart
+++ b/backend-dart/lib/application/service/dto/time_entry_dto.freezed.dart
@@ -22,7 +22,7 @@ TimeEntryDto _$TimeEntryDtoFromJson(Map<String, dynamic> json) {
 mixin _$TimeEntryDto {
   String get id => throw _privateConstructorUsedError;
   DateTime get startTime => throw _privateConstructorUsedError;
-  DateTime get endTime => throw _privateConstructorUsedError;
+  DateTime? get endTime => throw _privateConstructorUsedError;
   String? get description => throw _privateConstructorUsedError;
   String get userId => throw _privateConstructorUsedError;
   String get projectId => throw _privateConstructorUsedError;
@@ -48,7 +48,7 @@ abstract class $TimeEntryDtoCopyWith<$Res> {
   $Res call(
       {String id,
       DateTime startTime,
-      DateTime endTime,
+      DateTime? endTime,
       String? description,
       String userId,
       String projectId,
@@ -73,7 +73,7 @@ class _$TimeEntryDtoCopyWithImpl<$Res, $Val extends TimeEntryDto>
   $Res call({
     Object? id = null,
     Object? startTime = null,
-    Object? endTime = null,
+    Object? endTime = freezed,
     Object? description = freezed,
     Object? userId = null,
     Object? projectId = null,
@@ -89,10 +89,10 @@ class _$TimeEntryDtoCopyWithImpl<$Res, $Val extends TimeEntryDto>
           ? _value.startTime
           : startTime // ignore: cast_nullable_to_non_nullable
               as DateTime,
-      endTime: null == endTime
+      endTime: freezed == endTime
           ? _value.endTime
           : endTime // ignore: cast_nullable_to_non_nullable
-              as DateTime,
+              as DateTime?,
       description: freezed == description
           ? _value.description
           : description // ignore: cast_nullable_to_non_nullable
@@ -128,7 +128,7 @@ abstract class _$$TimeEntryDtoImplCopyWith<$Res>
   $Res call(
       {String id,
       DateTime startTime,
-      DateTime endTime,
+      DateTime? endTime,
       String? description,
       String userId,
       String projectId,
@@ -151,7 +151,7 @@ class __$$TimeEntryDtoImplCopyWithImpl<$Res>
   $Res call({
     Object? id = null,
     Object? startTime = null,
-    Object? endTime = null,
+    Object? endTime = freezed,
     Object? description = freezed,
     Object? userId = null,
     Object? projectId = null,
@@ -167,10 +167,10 @@ class __$$TimeEntryDtoImplCopyWithImpl<$Res>
           ? _value.startTime
           : startTime // ignore: cast_nullable_to_non_nullable
               as DateTime,
-      endTime: null == endTime
+      endTime: freezed == endTime
           ? _value.endTime
           : endTime // ignore: cast_nullable_to_non_nullable
-              as DateTime,
+              as DateTime?,
       description: freezed == description
           ? _value.description
           : description // ignore: cast_nullable_to_non_nullable
@@ -216,7 +216,7 @@ class _$TimeEntryDtoImpl implements _TimeEntryDto {
   @override
   final DateTime startTime;
   @override
-  final DateTime endTime;
+  final DateTime? endTime;
   @override
   final String? description;
   @override
@@ -278,7 +278,7 @@ abstract class _TimeEntryDto implements TimeEntryDto {
   const factory _TimeEntryDto(
       {required final String id,
       required final DateTime startTime,
-      required final DateTime endTime,
+      required final DateTime? endTime,
       final String? description,
       required final String userId,
       required final String projectId,
@@ -293,7 +293,7 @@ abstract class _TimeEntryDto implements TimeEntryDto {
   @override
   DateTime get startTime;
   @override
-  DateTime get endTime;
+  DateTime? get endTime;
   @override
   String? get description;
   @override
@@ -320,7 +320,7 @@ TimeEntryCreateDto _$TimeEntryCreateDtoFromJson(Map<String, dynamic> json) {
 /// @nodoc
 mixin _$TimeEntryCreateDto {
   DateTime get startTime => throw _privateConstructorUsedError;
-  DateTime get endTime => throw _privateConstructorUsedError;
+  DateTime? get endTime => throw _privateConstructorUsedError;
   String? get description => throw _privateConstructorUsedError;
   String get userId => throw _privateConstructorUsedError;
   String get projectId => throw _privateConstructorUsedError;
@@ -343,7 +343,7 @@ abstract class $TimeEntryCreateDtoCopyWith<$Res> {
   @useResult
   $Res call(
       {DateTime startTime,
-      DateTime endTime,
+      DateTime? endTime,
       String? description,
       String userId,
       String projectId});
@@ -365,7 +365,7 @@ class _$TimeEntryCreateDtoCopyWithImpl<$Res, $Val extends TimeEntryCreateDto>
   @override
   $Res call({
     Object? startTime = null,
-    Object? endTime = null,
+    Object? endTime = freezed,
     Object? description = freezed,
     Object? userId = null,
     Object? projectId = null,
@@ -375,10 +375,10 @@ class _$TimeEntryCreateDtoCopyWithImpl<$Res, $Val extends TimeEntryCreateDto>
           ? _value.startTime
           : startTime // ignore: cast_nullable_to_non_nullable
               as DateTime,
-      endTime: null == endTime
+      endTime: freezed == endTime
           ? _value.endTime
           : endTime // ignore: cast_nullable_to_non_nullable
-              as DateTime,
+              as DateTime?,
       description: freezed == description
           ? _value.description
           : description // ignore: cast_nullable_to_non_nullable
@@ -405,7 +405,7 @@ abstract class _$$TimeEntryCreateDtoImplCopyWith<$Res>
   @useResult
   $Res call(
       {DateTime startTime,
-      DateTime endTime,
+      DateTime? endTime,
       String? description,
       String userId,
       String projectId});
@@ -425,7 +425,7 @@ class __$$TimeEntryCreateDtoImplCopyWithImpl<$Res>
   @override
   $Res call({
     Object? startTime = null,
-    Object? endTime = null,
+    Object? endTime = freezed,
     Object? description = freezed,
     Object? userId = null,
     Object? projectId = null,
@@ -435,10 +435,10 @@ class __$$TimeEntryCreateDtoImplCopyWithImpl<$Res>
           ? _value.startTime
           : startTime // ignore: cast_nullable_to_non_nullable
               as DateTime,
-      endTime: null == endTime
+      endTime: freezed == endTime
           ? _value.endTime
           : endTime // ignore: cast_nullable_to_non_nullable
-              as DateTime,
+              as DateTime?,
       description: freezed == description
           ? _value.description
           : description // ignore: cast_nullable_to_non_nullable
@@ -460,7 +460,7 @@ class __$$TimeEntryCreateDtoImplCopyWithImpl<$Res>
 class _$TimeEntryCreateDtoImpl implements _TimeEntryCreateDto {
   const _$TimeEntryCreateDtoImpl(
       {required this.startTime,
-      required this.endTime,
+      this.endTime,
       this.description,
       required this.userId,
       required this.projectId});
@@ -471,7 +471,7 @@ class _$TimeEntryCreateDtoImpl implements _TimeEntryCreateDto {
   @override
   final DateTime startTime;
   @override
-  final DateTime endTime;
+  final DateTime? endTime;
   @override
   final String? description;
   @override
@@ -524,7 +524,7 @@ class _$TimeEntryCreateDtoImpl implements _TimeEntryCreateDto {
 abstract class _TimeEntryCreateDto implements TimeEntryCreateDto {
   const factory _TimeEntryCreateDto(
       {required final DateTime startTime,
-      required final DateTime endTime,
+      final DateTime? endTime,
       final String? description,
       required final String userId,
       required final String projectId}) = _$TimeEntryCreateDtoImpl;
@@ -535,7 +535,7 @@ abstract class _TimeEntryCreateDto implements TimeEntryCreateDto {
   @override
   DateTime get startTime;
   @override
-  DateTime get endTime;
+  DateTime? get endTime;
   @override
   String? get description;
   @override
diff --git a/backend-dart/lib/application/service/dto/time_entry_dto.g.dart b/backend-dart/lib/application/service/dto/time_entry_dto.g.dart
index 26722fc..88dd02d 100644
--- a/backend-dart/lib/application/service/dto/time_entry_dto.g.dart
+++ b/backend-dart/lib/application/service/dto/time_entry_dto.g.dart
@@ -10,7 +10,9 @@ _$TimeEntryDtoImpl _$$TimeEntryDtoImplFromJson(Map<String, dynamic> json) =>
     _$TimeEntryDtoImpl(
       id: json['id'] as String,
       startTime: DateTime.parse(json['startTime'] as String),
-      endTime: DateTime.parse(json['endTime'] as String),
+      endTime: json['endTime'] == null
+          ? null
+          : DateTime.parse(json['endTime'] as String),
       description: json['description'] as String?,
       userId: json['userId'] as String,
       projectId: json['projectId'] as String,
@@ -22,7 +24,7 @@ Map<String, dynamic> _$$TimeEntryDtoImplToJson(_$TimeEntryDtoImpl instance) =>
     <String, dynamic>{
       'id': instance.id,
       'startTime': instance.startTime.toIso8601String(),
-      'endTime': instance.endTime.toIso8601String(),
+      'endTime': instance.endTime?.toIso8601String(),
       'description': instance.description,
       'userId': instance.userId,
       'projectId': instance.projectId,
@@ -34,7 +36,9 @@ _$TimeEntryCreateDtoImpl _$$TimeEntryCreateDtoImplFromJson(
         Map<String, dynamic> json) =>
     _$TimeEntryCreateDtoImpl(
       startTime: DateTime.parse(json['startTime'] as String),
-      endTime: DateTime.parse(json['endTime'] as String),
+      endTime: json['endTime'] == null
+          ? null
+          : DateTime.parse(json['endTime'] as String),
       description: json['description'] as String?,
       userId: json['userId'] as String,
       projectId: json['projectId'] as String,
@@ -44,7 +48,7 @@ Map<String, dynamic> _$$TimeEntryCreateDtoImplToJson(
         _$TimeEntryCreateDtoImpl instance) =>
     <String, dynamic>{
       'startTime': instance.startTime.toIso8601String(),
-      'endTime': instance.endTime.toIso8601String(),
+      'endTime': instance.endTime?.toIso8601String(),
       'description': instance.description,
       'userId': instance.userId,
       'projectId': instance.projectId,
diff --git a/backend-dart/lib/domain/entities/time_entry.dart b/backend-dart/lib/domain/entities/time_entry.dart
index b7f233e..dc83e63 100644
--- a/backend-dart/lib/domain/entities/time_entry.dart
+++ b/backend-dart/lib/domain/entities/time_entry.dart
@@ -8,7 +8,7 @@ class TimeEntry with _$TimeEntry {
   const factory TimeEntry({
     required String id,
     required DateTime startTime,
-    required DateTime endTime,
+    required DateTime? endTime,
     String? description,
     required String userId,
     required String projectId,
@@ -25,7 +25,7 @@ class TimeEntryCreate with _$TimeEntryCreate {
   const factory TimeEntryCreate({
     String? id,
     required DateTime startTime,
-    required DateTime endTime,
+     DateTime? endTime,
     String? description,
     required String userId,
     required String projectId,
diff --git a/backend-dart/lib/domain/entities/time_entry.freezed.dart b/backend-dart/lib/domain/entities/time_entry.freezed.dart
index 044fd81..31c37ae 100644
--- a/backend-dart/lib/domain/entities/time_entry.freezed.dart
+++ b/backend-dart/lib/domain/entities/time_entry.freezed.dart
@@ -22,7 +22,7 @@ TimeEntry _$TimeEntryFromJson(Map<String, dynamic> json) {
 mixin _$TimeEntry {
   String get id => throw _privateConstructorUsedError;
   DateTime get startTime => throw _privateConstructorUsedError;
-  DateTime get endTime => throw _privateConstructorUsedError;
+  DateTime? get endTime => throw _privateConstructorUsedError;
   String? get description => throw _privateConstructorUsedError;
   String get userId => throw _privateConstructorUsedError;
   String get projectId => throw _privateConstructorUsedError;
@@ -47,7 +47,7 @@ abstract class $TimeEntryCopyWith<$Res> {
   $Res call(
       {String id,
       DateTime startTime,
-      DateTime endTime,
+      DateTime? endTime,
       String? description,
       String userId,
       String projectId,
@@ -72,7 +72,7 @@ class _$TimeEntryCopyWithImpl<$Res, $Val extends TimeEntry>
   $Res call({
     Object? id = null,
     Object? startTime = null,
-    Object? endTime = null,
+    Object? endTime = freezed,
     Object? description = freezed,
     Object? userId = null,
     Object? projectId = null,
@@ -88,10 +88,10 @@ class _$TimeEntryCopyWithImpl<$Res, $Val extends TimeEntry>
           ? _value.startTime
           : startTime // ignore: cast_nullable_to_non_nullable
               as DateTime,
-      endTime: null == endTime
+      endTime: freezed == endTime
           ? _value.endTime
           : endTime // ignore: cast_nullable_to_non_nullable
-              as DateTime,
+              as DateTime?,
       description: freezed == description
           ? _value.description
           : description // ignore: cast_nullable_to_non_nullable
@@ -127,7 +127,7 @@ abstract class _$$TimeEntryImplCopyWith<$Res>
   $Res call(
       {String id,
       DateTime startTime,
-      DateTime endTime,
+      DateTime? endTime,
       String? description,
       String userId,
       String projectId,
@@ -150,7 +150,7 @@ class __$$TimeEntryImplCopyWithImpl<$Res>
   $Res call({
     Object? id = null,
     Object? startTime = null,
-    Object? endTime = null,
+    Object? endTime = freezed,
     Object? description = freezed,
     Object? userId = null,
     Object? projectId = null,
@@ -166,10 +166,10 @@ class __$$TimeEntryImplCopyWithImpl<$Res>
           ? _value.startTime
           : startTime // ignore: cast_nullable_to_non_nullable
               as DateTime,
-      endTime: null == endTime
+      endTime: freezed == endTime
           ? _value.endTime
           : endTime // ignore: cast_nullable_to_non_nullable
-              as DateTime,
+              as DateTime?,
       description: freezed == description
           ? _value.description
           : description // ignore: cast_nullable_to_non_nullable
@@ -215,7 +215,7 @@ class _$TimeEntryImpl implements _TimeEntry {
   @override
   final DateTime startTime;
   @override
-  final DateTime endTime;
+  final DateTime? endTime;
   @override
   final String? description;
   @override
@@ -277,7 +277,7 @@ abstract class _TimeEntry implements TimeEntry {
   const factory _TimeEntry(
       {required final String id,
       required final DateTime startTime,
-      required final DateTime endTime,
+      required final DateTime? endTime,
       final String? description,
       required final String userId,
       required final String projectId,
@@ -292,7 +292,7 @@ abstract class _TimeEntry implements TimeEntry {
   @override
   DateTime get startTime;
   @override
-  DateTime get endTime;
+  DateTime? get endTime;
   @override
   String? get description;
   @override
@@ -320,7 +320,7 @@ TimeEntryCreate _$TimeEntryCreateFromJson(Map<String, dynamic> json) {
 mixin _$TimeEntryCreate {
   String? get id => throw _privateConstructorUsedError;
   DateTime get startTime => throw _privateConstructorUsedError;
-  DateTime get endTime => throw _privateConstructorUsedError;
+  DateTime? get endTime => throw _privateConstructorUsedError;
   String? get description => throw _privateConstructorUsedError;
   String get userId => throw _privateConstructorUsedError;
   String get projectId => throw _privateConstructorUsedError;
@@ -344,7 +344,7 @@ abstract class $TimeEntryCreateCopyWith<$Res> {
   $Res call(
       {String? id,
       DateTime startTime,
-      DateTime endTime,
+      DateTime? endTime,
       String? description,
       String userId,
       String projectId});
@@ -367,7 +367,7 @@ class _$TimeEntryCreateCopyWithImpl<$Res, $Val extends TimeEntryCreate>
   $Res call({
     Object? id = freezed,
     Object? startTime = null,
-    Object? endTime = null,
+    Object? endTime = freezed,
     Object? description = freezed,
     Object? userId = null,
     Object? projectId = null,
@@ -381,10 +381,10 @@ class _$TimeEntryCreateCopyWithImpl<$Res, $Val extends TimeEntryCreate>
           ? _value.startTime
           : startTime // ignore: cast_nullable_to_non_nullable
               as DateTime,
-      endTime: null == endTime
+      endTime: freezed == endTime
           ? _value.endTime
           : endTime // ignore: cast_nullable_to_non_nullable
-              as DateTime,
+              as DateTime?,
       description: freezed == description
           ? _value.description
           : description // ignore: cast_nullable_to_non_nullable
@@ -412,7 +412,7 @@ abstract class _$$TimeEntryCreateImplCopyWith<$Res>
   $Res call(
       {String? id,
       DateTime startTime,
-      DateTime endTime,
+      DateTime? endTime,
       String? description,
       String userId,
       String projectId});
@@ -433,7 +433,7 @@ class __$$TimeEntryCreateImplCopyWithImpl<$Res>
   $Res call({
     Object? id = freezed,
     Object? startTime = null,
-    Object? endTime = null,
+    Object? endTime = freezed,
     Object? description = freezed,
     Object? userId = null,
     Object? projectId = null,
@@ -447,10 +447,10 @@ class __$$TimeEntryCreateImplCopyWithImpl<$Res>
           ? _value.startTime
           : startTime // ignore: cast_nullable_to_non_nullable
               as DateTime,
-      endTime: null == endTime
+      endTime: freezed == endTime
           ? _value.endTime
           : endTime // ignore: cast_nullable_to_non_nullable
-              as DateTime,
+              as DateTime?,
       description: freezed == description
           ? _value.description
           : description // ignore: cast_nullable_to_non_nullable
@@ -473,7 +473,7 @@ class _$TimeEntryCreateImpl implements _TimeEntryCreate {
   const _$TimeEntryCreateImpl(
       {this.id,
       required this.startTime,
-      required this.endTime,
+      this.endTime,
       this.description,
       required this.userId,
       required this.projectId});
@@ -486,7 +486,7 @@ class _$TimeEntryCreateImpl implements _TimeEntryCreate {
   @override
   final DateTime startTime;
   @override
-  final DateTime endTime;
+  final DateTime? endTime;
   @override
   final String? description;
   @override
@@ -541,7 +541,7 @@ abstract class _TimeEntryCreate implements TimeEntryCreate {
   const factory _TimeEntryCreate(
       {final String? id,
       required final DateTime startTime,
-      required final DateTime endTime,
+      final DateTime? endTime,
       final String? description,
       required final String userId,
       required final String projectId}) = _$TimeEntryCreateImpl;
@@ -554,7 +554,7 @@ abstract class _TimeEntryCreate implements TimeEntryCreate {
   @override
   DateTime get startTime;
   @override
-  DateTime get endTime;
+  DateTime? get endTime;
   @override
   String? get description;
   @override
diff --git a/backend-dart/lib/domain/entities/time_entry.g.dart b/backend-dart/lib/domain/entities/time_entry.g.dart
index 7c78d1a..bec2232 100644
--- a/backend-dart/lib/domain/entities/time_entry.g.dart
+++ b/backend-dart/lib/domain/entities/time_entry.g.dart
@@ -10,7 +10,9 @@ _$TimeEntryImpl _$$TimeEntryImplFromJson(Map<String, dynamic> json) =>
     _$TimeEntryImpl(
       id: json['id'] as String,
       startTime: DateTime.parse(json['startTime'] as String),
-      endTime: DateTime.parse(json['endTime'] as String),
+      endTime: json['endTime'] == null
+          ? null
+          : DateTime.parse(json['endTime'] as String),
       description: json['description'] as String?,
       userId: json['userId'] as String,
       projectId: json['projectId'] as String,
@@ -22,7 +24,7 @@ Map<String, dynamic> _$$TimeEntryImplToJson(_$TimeEntryImpl instance) =>
     <String, dynamic>{
       'id': instance.id,
       'startTime': instance.startTime.toIso8601String(),
-      'endTime': instance.endTime.toIso8601String(),
+      'endTime': instance.endTime?.toIso8601String(),
       'description': instance.description,
       'userId': instance.userId,
       'projectId': instance.projectId,
@@ -35,7 +37,9 @@ _$TimeEntryCreateImpl _$$TimeEntryCreateImplFromJson(
     _$TimeEntryCreateImpl(
       id: json['id'] as String?,
       startTime: DateTime.parse(json['startTime'] as String),
-      endTime: DateTime.parse(json['endTime'] as String),
+      endTime: json['endTime'] == null
+          ? null
+          : DateTime.parse(json['endTime'] as String),
       description: json['description'] as String?,
       userId: json['userId'] as String,
       projectId: json['projectId'] as String,
@@ -46,7 +50,7 @@ Map<String, dynamic> _$$TimeEntryCreateImplToJson(
     <String, dynamic>{
       'id': instance.id,
       'startTime': instance.startTime.toIso8601String(),
-      'endTime': instance.endTime.toIso8601String(),
+      'endTime': instance.endTime?.toIso8601String(),
       'description': instance.description,
       'userId': instance.userId,
       'projectId': instance.projectId,
diff --git a/backend-dart/lib/infrastructure/persistence/db/client.dart b/backend-dart/lib/infrastructure/persistence/db/client.dart
index 5ce97cb..4c1ea1c 100755
--- a/backend-dart/lib/infrastructure/persistence/db/client.dart
+++ b/backend-dart/lib/infrastructure/persistence/db/client.dart
@@ -2363,7 +2363,7 @@ class PrismaClient extends _i1.BasePrismaClient<PrismaClient> {
             'name': 'endTime',
             'kind': 'scalar',
             'isList': false,
-            'isRequired': true,
+            'isRequired': false,
             'isUnique': false,
             'isId': false,
             'isReadOnly': false,
@@ -2680,7 +2680,7 @@ class PrismaClient extends _i1.BasePrismaClient<PrismaClient> {
   @override
   get $engine => _engine ??= _i5.BinaryEngine(
         schema:
-            'generator dartClient {\n  provider = "dart run orm"\n  output   = "../lib/infrastructure/persistence/db"\n}\n\ndatasource db {\n  provider = "postgresql"\n  url      = env("DATABASE_URL")\n}\n\n// User Model\nmodel UserDbo {\n  id          String         @id @default(uuid())\n  name        String\n  email       String         @unique\n  password    String\n  projects    ProjectDbo[] // Beziehung zu Projekten\n  timeEntries TimeEntryDbo[] // Beziehung zu Zeiteinträgen\n  createdAt   DateTime       @default(now())\n  updatedAt   DateTime       @updatedAt\n}\n\n// Project Model\nmodel ProjectDbo {\n  id          String           @id @default(uuid())\n  name        String\n  description String?\n  clientId    String?\n  tasks       ProjectTaskDbo[] // Beziehung zu Aufgaben\n  timeEntries TimeEntryDbo[] // Beziehung zu Zeiteinträgen\n  user        UserDbo          @relation(fields: [userId], references: [id])\n  userId      String\n  createdAt   DateTime         @default(now())\n  updatedAt   DateTime         @updatedAt\n}\n\n// TimeEntry Model\nmodel TimeEntryDbo {\n  id          String     @id @default(uuid())\n  startTime   DateTime\n  endTime     DateTime\n  description String?\n  user        UserDbo    @relation(fields: [userId], references: [id])\n  userId      String\n  project     ProjectDbo @relation(fields: [projectId], references: [id])\n  projectId   String\n  createdAt   DateTime   @default(now())\n  updatedAt   DateTime   @updatedAt\n}\n\n// Task Model (optional)\nmodel ProjectTaskDbo {\n  id          String     @id @default(uuid())\n  name        String\n  description String?\n  project     ProjectDbo @relation(fields: [projectId], references: [id])\n  projectId   String\n  createdAt   DateTime   @default(now())\n  updatedAt   DateTime   @updatedAt\n}\n',
+            'generator dartClient {\n  provider = "dart run orm"\n  output   = "../lib/infrastructure/persistence/db"\n}\n\ndatasource db {\n  provider = "postgresql"\n  url      = env("DATABASE_URL")\n}\n\n// User Model\nmodel UserDbo {\n  id          String         @id @default(uuid())\n  name        String\n  email       String         @unique\n  password    String\n  projects    ProjectDbo[] // Beziehung zu Projekten\n  timeEntries TimeEntryDbo[] // Beziehung zu Zeiteinträgen\n  createdAt   DateTime       @default(now())\n  updatedAt   DateTime       @updatedAt\n}\n\n// Project Model\nmodel ProjectDbo {\n  id          String           @id @default(uuid())\n  name        String\n  description String?\n  clientId    String?\n  tasks       ProjectTaskDbo[] // Beziehung zu Aufgaben\n  timeEntries TimeEntryDbo[] // Beziehung zu Zeiteinträgen\n  user        UserDbo          @relation(fields: [userId], references: [id])\n  userId      String\n  createdAt   DateTime         @default(now())\n  updatedAt   DateTime         @updatedAt\n}\n\n// TimeEntry Model\nmodel TimeEntryDbo {\n  id          String     @id @default(uuid())\n  startTime   DateTime\n  endTime     DateTime?\n  description String?\n  user        UserDbo    @relation(fields: [userId], references: [id])\n  userId      String\n  project     ProjectDbo @relation(fields: [projectId], references: [id])\n  projectId   String\n  createdAt   DateTime   @default(now())\n  updatedAt   DateTime   @updatedAt\n}\n\n// Task Model (optional)\nmodel ProjectTaskDbo {\n  id          String     @id @default(uuid())\n  name        String\n  description String?\n  project     ProjectDbo @relation(fields: [projectId], references: [id])\n  projectId   String\n  createdAt   DateTime   @default(now())\n  updatedAt   DateTime   @updatedAt\n}\n',
         datasources: const {
           'db': _i1.Datasource(
             _i1.DatasourceType.environment,
diff --git a/backend-dart/lib/infrastructure/persistence/db/prisma.dart b/backend-dart/lib/infrastructure/persistence/db/prisma.dart
index 146546c..ef4eeee 100755
--- a/backend-dart/lib/infrastructure/persistence/db/prisma.dart
+++ b/backend-dart/lib/infrastructure/persistence/db/prisma.dart
@@ -471,6 +471,100 @@ class ProjectTaskDboListRelationFilter
       };
 }
 
+class NestedDateTimeNullableFilter
+    implements _i1.JsonConvertible<Map<String, dynamic>> {
+  const NestedDateTimeNullableFilter({
+    this.equals,
+    this.$in,
+    this.notIn,
+    this.lt,
+    this.lte,
+    this.gt,
+    this.gte,
+    this.not,
+  });
+
+  final _i1.PrismaUnion<DateTime,
+      _i1.PrismaUnion<_i1.Reference<DateTime>, _i1.PrismaNull>>? equals;
+
+  final _i1.PrismaUnion<Iterable<DateTime>,
+      _i1.PrismaUnion<_i1.Reference<Iterable<DateTime>>, _i1.PrismaNull>>? $in;
+
+  final _i1.PrismaUnion<Iterable<DateTime>,
+          _i1.PrismaUnion<_i1.Reference<Iterable<DateTime>>, _i1.PrismaNull>>?
+      notIn;
+
+  final _i1.PrismaUnion<DateTime, _i1.Reference<DateTime>>? lt;
+
+  final _i1.PrismaUnion<DateTime, _i1.Reference<DateTime>>? lte;
+
+  final _i1.PrismaUnion<DateTime, _i1.Reference<DateTime>>? gt;
+
+  final _i1.PrismaUnion<DateTime, _i1.Reference<DateTime>>? gte;
+
+  final _i1.PrismaUnion<DateTime,
+      _i1.PrismaUnion<_i2.NestedDateTimeNullableFilter, _i1.PrismaNull>>? not;
+
+  @override
+  Map<String, dynamic> toJson() => {
+        'equals': equals,
+        'in': $in,
+        'notIn': notIn,
+        'lt': lt,
+        'lte': lte,
+        'gt': gt,
+        'gte': gte,
+        'not': not,
+      };
+}
+
+class DateTimeNullableFilter
+    implements _i1.JsonConvertible<Map<String, dynamic>> {
+  const DateTimeNullableFilter({
+    this.equals,
+    this.$in,
+    this.notIn,
+    this.lt,
+    this.lte,
+    this.gt,
+    this.gte,
+    this.not,
+  });
+
+  final _i1.PrismaUnion<DateTime,
+      _i1.PrismaUnion<_i1.Reference<DateTime>, _i1.PrismaNull>>? equals;
+
+  final _i1.PrismaUnion<Iterable<DateTime>,
+      _i1.PrismaUnion<_i1.Reference<Iterable<DateTime>>, _i1.PrismaNull>>? $in;
+
+  final _i1.PrismaUnion<Iterable<DateTime>,
+          _i1.PrismaUnion<_i1.Reference<Iterable<DateTime>>, _i1.PrismaNull>>?
+      notIn;
+
+  final _i1.PrismaUnion<DateTime, _i1.Reference<DateTime>>? lt;
+
+  final _i1.PrismaUnion<DateTime, _i1.Reference<DateTime>>? lte;
+
+  final _i1.PrismaUnion<DateTime, _i1.Reference<DateTime>>? gt;
+
+  final _i1.PrismaUnion<DateTime, _i1.Reference<DateTime>>? gte;
+
+  final _i1.PrismaUnion<DateTime,
+      _i1.PrismaUnion<_i2.NestedDateTimeNullableFilter, _i1.PrismaNull>>? not;
+
+  @override
+  Map<String, dynamic> toJson() => {
+        'equals': equals,
+        'in': $in,
+        'notIn': notIn,
+        'lt': lt,
+        'lte': lte,
+        'gt': gt,
+        'gte': gte,
+        'not': not,
+      };
+}
+
 class UserDboScalarRelationFilter
     implements _i1.JsonConvertible<Map<String, dynamic>> {
   const UserDboScalarRelationFilter({
@@ -519,7 +613,8 @@ class TimeEntryDboWhereInput
 
   final _i1.PrismaUnion<_i2.DateTimeFilter, DateTime>? startTime;
 
-  final _i1.PrismaUnion<_i2.DateTimeFilter, DateTime>? endTime;
+  final _i1.PrismaUnion<_i2.DateTimeNullableFilter,
+      _i1.PrismaUnion<DateTime, _i1.PrismaNull>>? endTime;
 
   final _i1.PrismaUnion<_i2.StringNullableFilter,
       _i1.PrismaUnion<String, _i1.PrismaNull>>? description;
@@ -1323,7 +1418,7 @@ class TimeEntryDboOrderByWithRelationInput
 
   final _i2.SortOrder? startTime;
 
-  final _i2.SortOrder? endTime;
+  final _i1.PrismaUnion<_i2.SortOrder, _i2.SortOrderInput>? endTime;
 
   final _i1.PrismaUnion<_i2.SortOrder, _i2.SortOrderInput>? description;
 
@@ -1384,7 +1479,8 @@ class TimeEntryDboWhereUniqueInput
 
   final _i1.PrismaUnion<_i2.DateTimeFilter, DateTime>? startTime;
 
-  final _i1.PrismaUnion<_i2.DateTimeFilter, DateTime>? endTime;
+  final _i1.PrismaUnion<_i2.DateTimeNullableFilter,
+      _i1.PrismaUnion<DateTime, _i1.PrismaNull>>? endTime;
 
   final _i1.PrismaUnion<_i2.StringNullableFilter,
       _i1.PrismaUnion<String, _i1.PrismaNull>>? description;
@@ -2100,7 +2196,7 @@ class TimeEntryDboUncheckedCreateWithoutProjectInput
   const TimeEntryDboUncheckedCreateWithoutProjectInput({
     this.id,
     required this.startTime,
-    required this.endTime,
+    this.endTime,
     this.description,
     required this.userId,
     this.createdAt,
@@ -2111,7 +2207,7 @@ class TimeEntryDboUncheckedCreateWithoutProjectInput
 
   final DateTime startTime;
 
-  final DateTime endTime;
+  final _i1.PrismaUnion<DateTime, _i1.PrismaNull>? endTime;
 
   final _i1.PrismaUnion<String, _i1.PrismaNull>? description;
 
@@ -2157,7 +2253,7 @@ class TimeEntryDboCreateManyProjectInput
   const TimeEntryDboCreateManyProjectInput({
     this.id,
     required this.startTime,
-    required this.endTime,
+    this.endTime,
     this.description,
     required this.userId,
     this.createdAt,
@@ -2168,7 +2264,7 @@ class TimeEntryDboCreateManyProjectInput
 
   final DateTime startTime;
 
-  final DateTime endTime;
+  final _i1.PrismaUnion<DateTime, _i1.PrismaNull>? endTime;
 
   final _i1.PrismaUnion<String, _i1.PrismaNull>? description;
 
@@ -2480,7 +2576,7 @@ class TimeEntryDboCreateWithoutProjectInput
   const TimeEntryDboCreateWithoutProjectInput({
     this.id,
     required this.startTime,
-    required this.endTime,
+    this.endTime,
     this.description,
     this.createdAt,
     this.updatedAt,
@@ -2491,7 +2587,7 @@ class TimeEntryDboCreateWithoutProjectInput
 
   final DateTime startTime;
 
-  final DateTime endTime;
+  final _i1.PrismaUnion<DateTime, _i1.PrismaNull>? endTime;
 
   final _i1.PrismaUnion<String, _i1.PrismaNull>? description;
 
@@ -2669,7 +2765,7 @@ class TimeEntryDboUncheckedCreateWithoutUserInput
   const TimeEntryDboUncheckedCreateWithoutUserInput({
     this.id,
     required this.startTime,
-    required this.endTime,
+    this.endTime,
     this.description,
     required this.projectId,
     this.createdAt,
@@ -2680,7 +2776,7 @@ class TimeEntryDboUncheckedCreateWithoutUserInput
 
   final DateTime startTime;
 
-  final DateTime endTime;
+  final _i1.PrismaUnion<DateTime, _i1.PrismaNull>? endTime;
 
   final _i1.PrismaUnion<String, _i1.PrismaNull>? description;
 
@@ -2726,7 +2822,7 @@ class TimeEntryDboCreateManyUserInput
   const TimeEntryDboCreateManyUserInput({
     this.id,
     required this.startTime,
-    required this.endTime,
+    this.endTime,
     this.description,
     required this.projectId,
     this.createdAt,
@@ -2737,7 +2833,7 @@ class TimeEntryDboCreateManyUserInput
 
   final DateTime startTime;
 
-  final DateTime endTime;
+  final _i1.PrismaUnion<DateTime, _i1.PrismaNull>? endTime;
 
   final _i1.PrismaUnion<String, _i1.PrismaNull>? description;
 
@@ -3024,7 +3120,7 @@ class TimeEntryDboCreateWithoutUserInput
   const TimeEntryDboCreateWithoutUserInput({
     this.id,
     required this.startTime,
-    required this.endTime,
+    this.endTime,
     this.description,
     this.createdAt,
     this.updatedAt,
@@ -3035,7 +3131,7 @@ class TimeEntryDboCreateWithoutUserInput
 
   final DateTime startTime;
 
-  final DateTime endTime;
+  final _i1.PrismaUnion<DateTime, _i1.PrismaNull>? endTime;
 
   final _i1.PrismaUnion<String, _i1.PrismaNull>? description;
 
@@ -3613,6 +3709,16 @@ class ProjectTaskDboUpdateManyWithoutProjectNestedInput
       };
 }
 
+class NullableDateTimeFieldUpdateOperationsInput
+    implements _i1.JsonConvertible<Map<String, dynamic>> {
+  const NullableDateTimeFieldUpdateOperationsInput({this.set});
+
+  final _i1.PrismaUnion<DateTime, _i1.PrismaNull>? set;
+
+  @override
+  Map<String, dynamic> toJson() => {'set': set};
+}
+
 class UserDboUpdateWithoutTimeEntriesInput
     implements _i1.JsonConvertible<Map<String, dynamic>> {
   const UserDboUpdateWithoutTimeEntriesInput({
@@ -3748,8 +3854,10 @@ class TimeEntryDboUncheckedUpdateWithoutProjectInput
   final _i1.PrismaUnion<DateTime, _i2.DateTimeFieldUpdateOperationsInput>?
       startTime;
 
-  final _i1.PrismaUnion<DateTime, _i2.DateTimeFieldUpdateOperationsInput>?
-      endTime;
+  final _i1.PrismaUnion<
+      DateTime,
+      _i1.PrismaUnion<_i2.NullableDateTimeFieldUpdateOperationsInput,
+          _i1.PrismaNull>>? endTime;
 
   final _i1.PrismaUnion<
       String,
@@ -3823,7 +3931,8 @@ class TimeEntryDboScalarWhereInput
 
   final _i1.PrismaUnion<_i2.DateTimeFilter, DateTime>? startTime;
 
-  final _i1.PrismaUnion<_i2.DateTimeFilter, DateTime>? endTime;
+  final _i1.PrismaUnion<_i2.DateTimeNullableFilter,
+      _i1.PrismaUnion<DateTime, _i1.PrismaNull>>? endTime;
 
   final _i1.PrismaUnion<_i2.StringNullableFilter,
       _i1.PrismaUnion<String, _i1.PrismaNull>>? description;
@@ -3868,8 +3977,10 @@ class TimeEntryDboUpdateManyMutationInput
   final _i1.PrismaUnion<DateTime, _i2.DateTimeFieldUpdateOperationsInput>?
       startTime;
 
-  final _i1.PrismaUnion<DateTime, _i2.DateTimeFieldUpdateOperationsInput>?
-      endTime;
+  final _i1.PrismaUnion<
+      DateTime,
+      _i1.PrismaUnion<_i2.NullableDateTimeFieldUpdateOperationsInput,
+          _i1.PrismaNull>>? endTime;
 
   final _i1.PrismaUnion<
       String,
@@ -3910,8 +4021,10 @@ class TimeEntryDboUncheckedUpdateManyWithoutProjectInput
   final _i1.PrismaUnion<DateTime, _i2.DateTimeFieldUpdateOperationsInput>?
       startTime;
 
-  final _i1.PrismaUnion<DateTime, _i2.DateTimeFieldUpdateOperationsInput>?
-      endTime;
+  final _i1.PrismaUnion<
+      DateTime,
+      _i1.PrismaUnion<_i2.NullableDateTimeFieldUpdateOperationsInput,
+          _i1.PrismaNull>>? endTime;
 
   final _i1.PrismaUnion<
       String,
@@ -4464,8 +4577,10 @@ class TimeEntryDboUpdateWithoutProjectInput
   final _i1.PrismaUnion<DateTime, _i2.DateTimeFieldUpdateOperationsInput>?
       startTime;
 
-  final _i1.PrismaUnion<DateTime, _i2.DateTimeFieldUpdateOperationsInput>?
-      endTime;
+  final _i1.PrismaUnion<
+      DateTime,
+      _i1.PrismaUnion<_i2.NullableDateTimeFieldUpdateOperationsInput,
+          _i1.PrismaNull>>? endTime;
 
   final _i1.PrismaUnion<
       String,
@@ -4793,8 +4908,10 @@ class TimeEntryDboUncheckedUpdateWithoutUserInput
   final _i1.PrismaUnion<DateTime, _i2.DateTimeFieldUpdateOperationsInput>?
       startTime;
 
-  final _i1.PrismaUnion<DateTime, _i2.DateTimeFieldUpdateOperationsInput>?
-      endTime;
+  final _i1.PrismaUnion<
+      DateTime,
+      _i1.PrismaUnion<_i2.NullableDateTimeFieldUpdateOperationsInput,
+          _i1.PrismaNull>>? endTime;
 
   final _i1.PrismaUnion<
       String,
@@ -4858,8 +4975,10 @@ class TimeEntryDboUncheckedUpdateManyWithoutUserInput
   final _i1.PrismaUnion<DateTime, _i2.DateTimeFieldUpdateOperationsInput>?
       startTime;
 
-  final _i1.PrismaUnion<DateTime, _i2.DateTimeFieldUpdateOperationsInput>?
-      endTime;
+  final _i1.PrismaUnion<
+      DateTime,
+      _i1.PrismaUnion<_i2.NullableDateTimeFieldUpdateOperationsInput,
+          _i1.PrismaNull>>? endTime;
 
   final _i1.PrismaUnion<
       String,
@@ -5288,8 +5407,10 @@ class TimeEntryDboUpdateWithoutUserInput
   final _i1.PrismaUnion<DateTime, _i2.DateTimeFieldUpdateOperationsInput>?
       startTime;
 
-  final _i1.PrismaUnion<DateTime, _i2.DateTimeFieldUpdateOperationsInput>?
-      endTime;
+  final _i1.PrismaUnion<
+      DateTime,
+      _i1.PrismaUnion<_i2.NullableDateTimeFieldUpdateOperationsInput,
+          _i1.PrismaNull>>? endTime;
 
   final _i1.PrismaUnion<
       String,
@@ -7839,7 +7960,7 @@ class TimeEntryDboCreateInput
   const TimeEntryDboCreateInput({
     this.id,
     required this.startTime,
-    required this.endTime,
+    this.endTime,
     this.description,
     this.createdAt,
     this.updatedAt,
@@ -7851,7 +7972,7 @@ class TimeEntryDboCreateInput
 
   final DateTime startTime;
 
-  final DateTime endTime;
+  final _i1.PrismaUnion<DateTime, _i1.PrismaNull>? endTime;
 
   final _i1.PrismaUnion<String, _i1.PrismaNull>? description;
 
@@ -7881,7 +8002,7 @@ class TimeEntryDboUncheckedCreateInput
   const TimeEntryDboUncheckedCreateInput({
     this.id,
     required this.startTime,
-    required this.endTime,
+    this.endTime,
     this.description,
     required this.userId,
     required this.projectId,
@@ -7893,7 +8014,7 @@ class TimeEntryDboUncheckedCreateInput
 
   final DateTime startTime;
 
-  final DateTime endTime;
+  final _i1.PrismaUnion<DateTime, _i1.PrismaNull>? endTime;
 
   final _i1.PrismaUnion<String, _i1.PrismaNull>? description;
 
@@ -7923,7 +8044,7 @@ class TimeEntryDboCreateManyInput
   const TimeEntryDboCreateManyInput({
     this.id,
     required this.startTime,
-    required this.endTime,
+    this.endTime,
     this.description,
     required this.userId,
     required this.projectId,
@@ -7935,7 +8056,7 @@ class TimeEntryDboCreateManyInput
 
   final DateTime startTime;
 
-  final DateTime endTime;
+  final _i1.PrismaUnion<DateTime, _i1.PrismaNull>? endTime;
 
   final _i1.PrismaUnion<String, _i1.PrismaNull>? description;
 
@@ -8088,8 +8209,10 @@ class TimeEntryDboUpdateInput
   final _i1.PrismaUnion<DateTime, _i2.DateTimeFieldUpdateOperationsInput>?
       startTime;
 
-  final _i1.PrismaUnion<DateTime, _i2.DateTimeFieldUpdateOperationsInput>?
-      endTime;
+  final _i1.PrismaUnion<
+      DateTime,
+      _i1.PrismaUnion<_i2.NullableDateTimeFieldUpdateOperationsInput,
+          _i1.PrismaNull>>? endTime;
 
   final _i1.PrismaUnion<
       String,
@@ -8137,8 +8260,10 @@ class TimeEntryDboUncheckedUpdateInput
   final _i1.PrismaUnion<DateTime, _i2.DateTimeFieldUpdateOperationsInput>?
       startTime;
 
-  final _i1.PrismaUnion<DateTime, _i2.DateTimeFieldUpdateOperationsInput>?
-      endTime;
+  final _i1.PrismaUnion<
+      DateTime,
+      _i1.PrismaUnion<_i2.NullableDateTimeFieldUpdateOperationsInput,
+          _i1.PrismaNull>>? endTime;
 
   final _i1.PrismaUnion<
       String,
@@ -8187,8 +8312,10 @@ class TimeEntryDboUncheckedUpdateManyInput
   final _i1.PrismaUnion<DateTime, _i2.DateTimeFieldUpdateOperationsInput>?
       startTime;
 
-  final _i1.PrismaUnion<DateTime, _i2.DateTimeFieldUpdateOperationsInput>?
-      endTime;
+  final _i1.PrismaUnion<
+      DateTime,
+      _i1.PrismaUnion<_i2.NullableDateTimeFieldUpdateOperationsInput,
+          _i1.PrismaNull>>? endTime;
 
   final _i1.PrismaUnion<
       String,
@@ -8647,7 +8774,7 @@ class TimeEntryDboOrderByWithAggregationInput
 
   final _i2.SortOrder? startTime;
 
-  final _i2.SortOrder? endTime;
+  final _i1.PrismaUnion<_i2.SortOrder, _i2.SortOrderInput>? endTime;
 
   final _i1.PrismaUnion<_i2.SortOrder, _i2.SortOrderInput>? description;
 
@@ -8681,6 +8808,128 @@ class TimeEntryDboOrderByWithAggregationInput
       };
 }
 
+class NestedDateTimeNullableWithAggregatesFilter
+    implements _i1.JsonConvertible<Map<String, dynamic>> {
+  const NestedDateTimeNullableWithAggregatesFilter({
+    this.equals,
+    this.$in,
+    this.notIn,
+    this.lt,
+    this.lte,
+    this.gt,
+    this.gte,
+    this.not,
+    this.$count,
+    this.$min,
+    this.$max,
+  });
+
+  final _i1.PrismaUnion<DateTime,
+      _i1.PrismaUnion<_i1.Reference<DateTime>, _i1.PrismaNull>>? equals;
+
+  final _i1.PrismaUnion<Iterable<DateTime>,
+      _i1.PrismaUnion<_i1.Reference<Iterable<DateTime>>, _i1.PrismaNull>>? $in;
+
+  final _i1.PrismaUnion<Iterable<DateTime>,
+          _i1.PrismaUnion<_i1.Reference<Iterable<DateTime>>, _i1.PrismaNull>>?
+      notIn;
+
+  final _i1.PrismaUnion<DateTime, _i1.Reference<DateTime>>? lt;
+
+  final _i1.PrismaUnion<DateTime, _i1.Reference<DateTime>>? lte;
+
+  final _i1.PrismaUnion<DateTime, _i1.Reference<DateTime>>? gt;
+
+  final _i1.PrismaUnion<DateTime, _i1.Reference<DateTime>>? gte;
+
+  final _i1.PrismaUnion<
+      DateTime,
+      _i1.PrismaUnion<_i2.NestedDateTimeNullableWithAggregatesFilter,
+          _i1.PrismaNull>>? not;
+
+  final _i2.NestedIntNullableFilter? $count;
+
+  final _i2.NestedDateTimeNullableFilter? $min;
+
+  final _i2.NestedDateTimeNullableFilter? $max;
+
+  @override
+  Map<String, dynamic> toJson() => {
+        'equals': equals,
+        'in': $in,
+        'notIn': notIn,
+        'lt': lt,
+        'lte': lte,
+        'gt': gt,
+        'gte': gte,
+        'not': not,
+        '_count': $count,
+        '_min': $min,
+        '_max': $max,
+      };
+}
+
+class DateTimeNullableWithAggregatesFilter
+    implements _i1.JsonConvertible<Map<String, dynamic>> {
+  const DateTimeNullableWithAggregatesFilter({
+    this.equals,
+    this.$in,
+    this.notIn,
+    this.lt,
+    this.lte,
+    this.gt,
+    this.gte,
+    this.not,
+    this.$count,
+    this.$min,
+    this.$max,
+  });
+
+  final _i1.PrismaUnion<DateTime,
+      _i1.PrismaUnion<_i1.Reference<DateTime>, _i1.PrismaNull>>? equals;
+
+  final _i1.PrismaUnion<Iterable<DateTime>,
+      _i1.PrismaUnion<_i1.Reference<Iterable<DateTime>>, _i1.PrismaNull>>? $in;
+
+  final _i1.PrismaUnion<Iterable<DateTime>,
+          _i1.PrismaUnion<_i1.Reference<Iterable<DateTime>>, _i1.PrismaNull>>?
+      notIn;
+
+  final _i1.PrismaUnion<DateTime, _i1.Reference<DateTime>>? lt;
+
+  final _i1.PrismaUnion<DateTime, _i1.Reference<DateTime>>? lte;
+
+  final _i1.PrismaUnion<DateTime, _i1.Reference<DateTime>>? gt;
+
+  final _i1.PrismaUnion<DateTime, _i1.Reference<DateTime>>? gte;
+
+  final _i1.PrismaUnion<
+      DateTime,
+      _i1.PrismaUnion<_i2.NestedDateTimeNullableWithAggregatesFilter,
+          _i1.PrismaNull>>? not;
+
+  final _i2.NestedIntNullableFilter? $count;
+
+  final _i2.NestedDateTimeNullableFilter? $min;
+
+  final _i2.NestedDateTimeNullableFilter? $max;
+
+  @override
+  Map<String, dynamic> toJson() => {
+        'equals': equals,
+        'in': $in,
+        'notIn': notIn,
+        'lt': lt,
+        'lte': lte,
+        'gt': gt,
+        'gte': gte,
+        'not': not,
+        '_count': $count,
+        '_min': $min,
+        '_max': $max,
+      };
+}
+
 class TimeEntryDboScalarWhereWithAggregatesInput
     implements _i1.JsonConvertible<Map<String, dynamic>> {
   const TimeEntryDboScalarWhereWithAggregatesInput({
@@ -8709,7 +8958,8 @@ class TimeEntryDboScalarWhereWithAggregatesInput
 
   final _i1.PrismaUnion<_i2.DateTimeWithAggregatesFilter, DateTime>? startTime;
 
-  final _i1.PrismaUnion<_i2.DateTimeWithAggregatesFilter, DateTime>? endTime;
+  final _i1.PrismaUnion<_i2.DateTimeNullableWithAggregatesFilter,
+      _i1.PrismaUnion<DateTime, _i1.PrismaNull>>? endTime;
 
   final _i1.PrismaUnion<_i2.StringNullableWithAggregatesFilter,
       _i1.PrismaUnion<String, _i1.PrismaNull>>? description;
diff --git a/backend-dart/lib/infrastructure/persistence/mapper/time_entry_dbo_mapper.dart b/backend-dart/lib/infrastructure/persistence/mapper/time_entry_dbo_mapper.dart
index 5c4f5fb..5e6f75d 100644
--- a/backend-dart/lib/infrastructure/persistence/mapper/time_entry_dbo_mapper.dart
+++ b/backend-dart/lib/infrastructure/persistence/mapper/time_entry_dbo_mapper.dart
@@ -29,7 +29,7 @@ class TimeEntryDboMapper {
       TaskEither.of(TimeEntryDboCreateInput(
         id: origin.id,
         startTime: origin.startTime,
-        endTime: origin.endTime,
+        endTime: origin.endTime.let(PrismaUnion.$1),
         description: origin.description.let(PrismaUnion.$1),
         user: UserDboCreateNestedOneWithoutTimeEntriesInput(
           connect: UserDboWhereUniqueInput(
diff --git a/backend-dart/prisma/schema.prisma b/backend-dart/prisma/schema.prisma
index 6f3b137..730b2b4 100755
--- a/backend-dart/prisma/schema.prisma
+++ b/backend-dart/prisma/schema.prisma
@@ -38,7 +38,7 @@ model ProjectDbo {
 model TimeEntryDbo {
   id          String   @id @default(uuid())
   startTime   DateTime
-  endTime     DateTime
+  endTime     DateTime?
   description String?
   user        UserDbo     @relation(fields: [userId], references: [id])
   userId      String