Store the date a build is created

src/Jackett.Common/Jackett.Common.csproj

@@ -211,4 +211,11 @@
     </EmbeddedResource>
   </ItemGroup>
 
+  <!-- Save the compiled date so that we know if the user is running an old version of Jackett -->
+  <ItemGroup>
+    <AssemblyAttribute Include="Jackett.Common.Utils.BuildDateAttribute">
+      <_Parameter1>$([System.DateTime]::UtcNow.ToString("yyyyMMddHHmmss"))</_Parameter1>
+    </AssemblyAttribute>
+  </ItemGroup>
+  
 </Project>

src/Jackett.Common/Utils/BuildDate.cs

@@ -0,0 +1,27 @@
+using System;
+using System.Globalization;
+using System.Reflection;
+
+namespace Jackett.Common.Utils
+{
+    public static class BuildDate
+    {
+        public static DateTime GetBuildDateTime()
+        {
+            Assembly commonAssembly = Assembly.GetExecutingAssembly();
+            var attribute = commonAssembly.GetCustomAttribute<BuildDateAttribute>();
+            return attribute?.DateTime ?? default(DateTime);
+        }
+    }
+
+    [AttributeUsage(AttributeTargets.Assembly)]
+    public class BuildDateAttribute : Attribute
+    {
+        public BuildDateAttribute(string value)
+        {
+            DateTime = DateTime.ParseExact(value, "yyyyMMddHHmmss", CultureInfo.InvariantCulture, DateTimeStyles.AssumeUniversal);
+        }
+
+        public DateTime DateTime { get; }
+    }
+}

src/Jackett.Server/Services/ServerService.cs

@@ -261,14 +261,9 @@ namespace Jackett.Server.Services
             //Warn user that they are using an old version of Jackett
             try
             {
-                string appFolder = configService.ApplicationFolder();
+                DateTime compiledData = BuildDate.GetBuildDateTime();
-                string dllPath = Path.Combine(appFolder, "Jackett.Common.dll");
 
-                if (File.Exists(dllPath))
+                if (compiledData < DateTime.Now.AddMonths(-3))
-                {
-                    DateTime creation = File.GetCreationTime(dllPath);
-
-                    if (creation < DateTime.Now.AddMonths(-3))
                 {
                     string version = configService.GetVersion();
                     string notice = $"Your version of Jackett v{version} is very old. Multiple indexers are likely to fail when using an old version. Update to the latest version of Jackett.";
@@ -276,7 +271,6 @@ namespace Jackett.Server.Services
                     logger.Error(notice);
                 }
             }
-            }
             catch (Exception e)
             {
                 logger.Error(e, "Error while checking build date of Jackett.Common");