diff --git a/Clockodo.NET/ClockodoService.cs b/Clockodo.NET/ClockodoService.cs
index 61059ef..8928cec 100644
--- a/Clockodo.NET/ClockodoService.cs
+++ b/Clockodo.NET/ClockodoService.cs
@@ -1,13 +1,14 @@
 using System.Collections.Immutable;
 using Clockodo.NET.DataContracts;
 using Clockodo.NET.Filter;
+using Newtonsoft.Json;
 
 namespace Clockodo.NET;
 
 public class ClockodoService : ITimeEntryService
 {
-    private readonly JsonSerializerSettings _jsonSettings;
     private readonly HttpClient _client;
+    private readonly JsonSerializerSettings _jsonSettings;
 
     public ClockodoService(Credentials credentials)
     {
diff --git a/Clockodo.NET/DataContracts/RawTimeEntry.cs b/Clockodo.NET/DataContracts/RawTimeEntry.cs
index f82f25f..3722a86 100644
--- a/Clockodo.NET/DataContracts/RawTimeEntry.cs
+++ b/Clockodo.NET/DataContracts/RawTimeEntry.cs
@@ -1,4 +1,6 @@
-namespace Clockodo.NET.DataContracts;
+using Newtonsoft.Json;
+
+namespace Clockodo.NET.DataContracts;
 
 public class RawTimeEntry
 {
diff --git a/Clockodo.NET/DataContracts/TimeEntry.cs b/Clockodo.NET/DataContracts/TimeEntry.cs
index 296c6bc..74030f1 100644
--- a/Clockodo.NET/DataContracts/TimeEntry.cs
+++ b/Clockodo.NET/DataContracts/TimeEntry.cs
@@ -14,18 +14,13 @@ internal TimeEntry(RawTimeEntry rawTimeEntry)
         ServicesName = rawTimeEntry.ServiceName;
     }
 
-    public TimeEntry()
-    {
-        
-    }
-
-    public DateTime Start { get; set; }
-    public DateTime End { get; set; }
-    public int Duration { get; set; }
+    public DateTime Start { get; }
+    public DateTime End { get; }
+    public int Duration { get; }
 
-    public string CustomerName { get; set; }
-    public string ProjectName { get; set; }
-    public string EmployeeName { get; set; }
-    public decimal Revenue { get; set; }
-    public string ServicesName { get; set; }
+    public string CustomerName { get; }
+    public string ProjectName { get; }
+    public string EmployeeName { get; }
+    public decimal Revenue { get; }
+    public string ServicesName { get; }
 }
\ No newline at end of file
diff --git a/Clockodo.NET/DataContracts/TimeEntryPaging.cs b/Clockodo.NET/DataContracts/TimeEntryPaging.cs
index dd26e1e..777cecd 100644
--- a/Clockodo.NET/DataContracts/TimeEntryPaging.cs
+++ b/Clockodo.NET/DataContracts/TimeEntryPaging.cs
@@ -1,4 +1,6 @@
-namespace Clockodo.NET.DataContracts
+using Newtonsoft.Json;
+
+namespace Clockodo.NET.DataContracts
 {
     internal class TimeEntryPaging
     {
diff --git a/Clockodo.NET/Filter/YearFilter.cs b/Clockodo.NET/Filter/YearFilter.cs
index d59b86b..d173439 100644
--- a/Clockodo.NET/Filter/YearFilter.cs
+++ b/Clockodo.NET/Filter/YearFilter.cs
@@ -1,19 +1,18 @@
 using Clockodo.NET.DataContracts;
 
-namespace Clockodo.NET.Filter
+namespace Clockodo.NET.Filter;
+
+public class YearFilter : IFilterTimeEntries
 {
-    public class YearFilter : IFilterTimeEntries
-    {
-        private readonly string _year;
+    private readonly string _year;
 
-        public YearFilter(string year)
-        {
-            _year = year;
-        }
+    public YearFilter(string year)
+    {
+        _year = year;
+    }
 
-        public IEnumerable<TimeEntry> Filter(IEnumerable<TimeEntry> source)
-        {
-            return source.Where(entry => entry.Start.Year.ToString() == _year);
-        }
+    public IEnumerable<TimeEntry> Filter(IEnumerable<TimeEntry> source)
+    {
+        return source.Where(entry => entry.Start.Year.ToString() == _year);
     }
-}
+}
\ No newline at end of file