diff --git a/.flake8 b/.flake8
new file mode 100644
index 0000000..04ca400
--- /dev/null
+++ b/.flake8
@@ -0,0 +1,18 @@
+[flake8]
+max-line-length = 88
+select = E,W,F,C,N
+ignore = E203,E501,W503
+exclude = 
+    .git,
+    __pycache__,
+    build,
+    dist, 
+    .eggs,
+    *.egg-info,
+    .venv,
+    venv,
+    .tox
+per-file-ignores = 
+    tests/*:F401,F811
+    __init__.py:F401
+max-complexity = 10
\ No newline at end of file
diff --git a/wikijs/endpoints/pages.py b/wikijs/endpoints/pages.py
index 306f618..8f36816 100644
--- a/wikijs/endpoints/pages.py
+++ b/wikijs/endpoints/pages.py
@@ -110,7 +110,7 @@ class PagesEndpoint(BaseEndpoint):
         """
 
         # Build variables object
-        variables = {}
+        variables: Dict[str, Any] = {}
         if limit is not None:
             variables["limit"] = limit
         if offset is not None:
@@ -129,10 +129,10 @@ class PagesEndpoint(BaseEndpoint):
             variables["orderDirection"] = order_direction
 
         # Make request with query and variables
-        json_data = {"query": query}
+        json_data: Dict[str, Any] = {"query": query}
         if variables:
             json_data["variables"] = variables
-        
+
         response = self._post("/graphql", json_data=json_data)
 
         # Parse response
diff --git a/wikijs/models/base.py b/wikijs/models/base.py
index 70b58cf..678e471 100644
--- a/wikijs/models/base.py
+++ b/wikijs/models/base.py
@@ -4,7 +4,7 @@ from datetime import datetime
 from typing import Any, Dict, Optional
 
 from pydantic import BaseModel as PydanticBaseModel
-from pydantic import ConfigDict
+from pydantic import ConfigDict, field_serializer
 
 
 class BaseModel(PydanticBaseModel):
@@ -26,8 +26,6 @@ class BaseModel(PydanticBaseModel):
         use_enum_values=True,
         # Allow extra fields for forward compatibility
         extra="ignore",
-        # Serialize datetime as ISO format
-        json_encoders={datetime: lambda v: v.isoformat() if v else None},
     )
 
     def to_dict(self, exclude_none: bool = True) -> Dict[str, Any]:
@@ -83,6 +81,11 @@ class TimestampedModel(BaseModel):
     created_at: Optional[datetime] = None
     updated_at: Optional[datetime] = None
 
+    @field_serializer('created_at', 'updated_at')
+    def serialize_datetime(self, value: Optional[datetime]) -> Optional[str]:
+        """Serialize datetime to ISO format."""
+        return value.isoformat() if value else None
+
     @property
     def is_new(self) -> bool:
         """Check if this is a new (unsaved) model."""
diff --git a/wikijs/models/page.py b/wikijs/models/page.py
index 493e782..e626bf8 100644
--- a/wikijs/models/page.py
+++ b/wikijs/models/page.py
@@ -3,7 +3,7 @@
 import re
 from typing import List, Optional
 
-from pydantic import Field, validator
+from pydantic import Field, field_validator
 
 from .base import BaseModel, TimestampedModel
 
@@ -37,7 +37,8 @@ class Page(TimestampedModel):
     # Editor information
     editor: Optional[str] = Field(None, description="Editor used")
 
-    @validator("path")
+    @field_validator("path")
+    @classmethod
     def validate_path(cls, v: str) -> str:
         """Validate page path format."""
         if not v:
@@ -52,7 +53,8 @@ class Page(TimestampedModel):
 
         return v
 
-    @validator("title")
+    @field_validator("title")
+    @classmethod
     def validate_title(cls, v: str) -> str:
         """Validate page title."""
         if not v or not v.strip():
@@ -132,7 +134,8 @@ class PageCreate(BaseModel):
     locale: str = Field("en", description="Page locale")
     editor: str = Field("markdown", description="Editor to use")
 
-    @validator("path")
+    @field_validator("path")
+    @classmethod
     def validate_path(cls, v: str) -> str:
         """Validate page path format."""
         if not v:
@@ -147,7 +150,8 @@ class PageCreate(BaseModel):
 
         return v
 
-    @validator("title")
+    @field_validator("title")
+    @classmethod
     def validate_title(cls, v: str) -> str:
         """Validate page title."""
         if not v or not v.strip():
@@ -172,7 +176,8 @@ class PageUpdate(BaseModel):
 
     tags: Optional[List[str]] = Field(None, description="Page tags")
 
-    @validator("title")
+    @field_validator("title")
+    @classmethod
     def validate_title(cls, v: Optional[str]) -> Optional[str]:
         """Validate page title if provided."""
         if v is not None: