diff --git a/src/Squidex.Domain.Apps.Core.Operations/GenerateJsonSchema/Builder.cs b/src/Squidex.Domain.Apps.Core.Operations/GenerateJsonSchema/Builder.cs
index 203c393f1..7dd06404f 100644
--- a/src/Squidex.Domain.Apps.Core.Operations/GenerateJsonSchema/Builder.cs
+++ b/src/Squidex.Domain.Apps.Core.Operations/GenerateJsonSchema/Builder.cs
@@ -38,7 +38,7 @@ namespace Squidex.Domain.Apps.Core.GenerateJsonSchema
 
         public static JsonProperty DateTimeProperty(string description = null, bool isRequired = false)
         {
-            return new JsonProperty { Type = JsonObjectType.Number, Format = JsonFormatStrings.DateTime, Description = description, IsRequired = isRequired };
+            return new JsonProperty { Type = JsonObjectType.String, Format = JsonFormatStrings.DateTime, Description = description, IsRequired = isRequired };
         }
 
         public static JsonProperty GuidProperty(string description = null, bool isRequired = false)