diff --git a/app/crud/todo.py b/app/crud/todo.py
index 1521e52..d49f205 100644
--- a/app/crud/todo.py
+++ b/app/crud/todo.py
@@ -1,9 +1,21 @@
 from typing import List, Optional, Tuple
+from datetime import datetime
 from sqlalchemy.orm import Session
+from sqlalchemy import and_, or_
 
 from app.models.todo import Todo, Priority
 from app.models.tag import Tag
 from app.schemas.todo import TodoCreate, TodoUpdate, SubtaskCreate
+from app.utils.date_utils import (
+    get_timezone_aware_now,
+    get_date_range_today,
+    get_date_range_this_week,
+    get_date_range_next_week,
+    get_date_range_next_days,
+    get_overdue_cutoff,
+    get_due_soon_cutoff,
+    is_overdue,
+)
 
 
 def get_todo(db: Session, todo_id: int) -> Optional[Todo]:
@@ -21,6 +33,11 @@ def get_todos(
     project_id: Optional[int] = None,
     parent_id: Optional[int] = None,
     include_subtasks: bool = True,
+    due_date_filter: Optional[str] = None,
+    overdue: Optional[bool] = None,
+    sort_by_due_date: bool = False,
+    due_date_start: Optional[datetime] = None,
+    due_date_end: Optional[datetime] = None,
 ) -> Tuple[List[Todo], int]:
     query = db.query(Todo)
 
@@ -45,11 +62,197 @@ def get_todos(
             Todo.title.contains(search) | Todo.description.contains(search)
         )
 
+    # Due date filtering
+    if due_date_filter:
+        if due_date_filter == "today":
+            start_date, end_date = get_date_range_today()
+            query = query.filter(
+                and_(Todo.due_date >= start_date, Todo.due_date <= end_date)
+            )
+        elif due_date_filter == "this_week":
+            start_date, end_date = get_date_range_this_week()
+            query = query.filter(
+                and_(Todo.due_date >= start_date, Todo.due_date <= end_date)
+            )
+        elif due_date_filter == "next_week":
+            start_date, end_date = get_date_range_next_week()
+            query = query.filter(
+                and_(Todo.due_date >= start_date, Todo.due_date <= end_date)
+            )
+
+    # Custom date range filtering
+    if due_date_start:
+        query = query.filter(Todo.due_date >= due_date_start)
+    if due_date_end:
+        query = query.filter(Todo.due_date <= due_date_end)
+
+    # Overdue filtering
+    if overdue is not None:
+        current_time = get_overdue_cutoff()
+        if overdue:
+            query = query.filter(
+                and_(Todo.due_date.isnot(None), Todo.due_date < current_time)
+            )
+        else:
+            query = query.filter(
+                or_(Todo.due_date.is_(None), Todo.due_date >= current_time)
+            )
+
     # Get total count before pagination
     total = query.count()
 
     # Apply pagination and ordering
-    todos = query.order_by(Todo.created_at.desc()).offset(skip).limit(limit).all()
+    if sort_by_due_date:
+        # Sort by due_date ascending (earliest first), with None values at the end
+        todos = (
+            query.order_by(Todo.due_date.asc().nullslast(), Todo.created_at.desc())
+            .offset(skip)
+            .limit(limit)
+            .all()
+        )
+    else:
+        todos = query.order_by(Todo.created_at.desc()).offset(skip).limit(limit).all()
+
+    return todos, total
+
+
+def get_overdue_todos(
+    db: Session,
+    skip: int = 0,
+    limit: int = 100,
+    completed: Optional[bool] = None,
+    priority: Optional[Priority] = None,
+    category_id: Optional[int] = None,
+    project_id: Optional[int] = None,
+    parent_id: Optional[int] = None,
+    include_subtasks: bool = True,
+) -> Tuple[List[Todo], int]:
+    """Get all overdue todos."""
+    current_time = get_overdue_cutoff()
+    query = db.query(Todo).filter(
+        and_(Todo.due_date.isnot(None), Todo.due_date < current_time)
+    )
+
+    # Apply same filtering logic as get_todos
+    if parent_id is not None:
+        query = query.filter(Todo.parent_id == parent_id)
+    elif not include_subtasks:
+        query = query.filter(Todo.parent_id.is_(None))
+
+    if completed is not None:
+        query = query.filter(Todo.completed == completed)
+    if priority is not None:
+        query = query.filter(Todo.priority == priority)
+    if category_id is not None:
+        query = query.filter(Todo.category_id == category_id)
+    if project_id is not None:
+        query = query.filter(Todo.project_id == project_id)
+
+    total = query.count()
+    todos = (
+        query.order_by(Todo.due_date.asc(), Todo.created_at.desc())
+        .offset(skip)
+        .limit(limit)
+        .all()
+    )
+
+    return todos, total
+
+
+def get_todos_due_soon(
+    db: Session,
+    days: int = 7,
+    skip: int = 0,
+    limit: int = 100,
+    completed: Optional[bool] = None,
+    priority: Optional[Priority] = None,
+    category_id: Optional[int] = None,
+    project_id: Optional[int] = None,
+    parent_id: Optional[int] = None,
+    include_subtasks: bool = True,
+) -> Tuple[List[Todo], int]:
+    """Get todos due within the next N days (default 7 days)."""
+    current_time = get_timezone_aware_now()
+    future_cutoff = get_due_soon_cutoff(days)
+    
+    query = db.query(Todo).filter(
+        and_(
+            Todo.due_date.isnot(None),
+            Todo.due_date >= current_time,
+            Todo.due_date <= future_cutoff,
+        )
+    )
+
+    # Apply same filtering logic as get_todos
+    if parent_id is not None:
+        query = query.filter(Todo.parent_id == parent_id)
+    elif not include_subtasks:
+        query = query.filter(Todo.parent_id.is_(None))
+
+    if completed is not None:
+        query = query.filter(Todo.completed == completed)
+    if priority is not None:
+        query = query.filter(Todo.priority == priority)
+    if category_id is not None:
+        query = query.filter(Todo.category_id == category_id)
+    if project_id is not None:
+        query = query.filter(Todo.project_id == project_id)
+
+    total = query.count()
+    todos = (
+        query.order_by(Todo.due_date.asc(), Todo.created_at.desc())
+        .offset(skip)
+        .limit(limit)
+        .all()
+    )
+
+    return todos, total
+
+
+def get_todos_by_date_range(
+    db: Session,
+    start_date: datetime,
+    end_date: datetime,
+    skip: int = 0,
+    limit: int = 100,
+    completed: Optional[bool] = None,
+    priority: Optional[Priority] = None,
+    category_id: Optional[int] = None,
+    project_id: Optional[int] = None,
+    parent_id: Optional[int] = None,
+    include_subtasks: bool = True,
+) -> Tuple[List[Todo], int]:
+    """Get todos within a specific date range."""
+    query = db.query(Todo).filter(
+        and_(
+            Todo.due_date.isnot(None),
+            Todo.due_date >= start_date,
+            Todo.due_date <= end_date,
+        )
+    )
+
+    # Apply same filtering logic as get_todos
+    if parent_id is not None:
+        query = query.filter(Todo.parent_id == parent_id)
+    elif not include_subtasks:
+        query = query.filter(Todo.parent_id.is_(None))
+
+    if completed is not None:
+        query = query.filter(Todo.completed == completed)
+    if priority is not None:
+        query = query.filter(Todo.priority == priority)
+    if category_id is not None:
+        query = query.filter(Todo.category_id == category_id)
+    if project_id is not None:
+        query = query.filter(Todo.project_id == project_id)
+
+    total = query.count()
+    todos = (
+        query.order_by(Todo.due_date.asc(), Todo.created_at.desc())
+        .offset(skip)
+        .limit(limit)
+        .all()
+    )
 
     return todos, total
 
diff --git a/app/schemas/__init__.py b/app/schemas/__init__.py
index 7b472da..f85fc6f 100644
--- a/app/schemas/__init__.py
+++ b/app/schemas/__init__.py
@@ -1,4 +1,4 @@
-from .todo import Todo, TodoCreate, TodoUpdate, TodoListResponse
+from .todo import Todo, TodoBase, TodoCreate, TodoUpdate, TodoListResponse
 from .category import Category, CategoryCreate, CategoryUpdate
 from .project import (
     Project,
@@ -10,6 +10,7 @@ from .project import (
 
 __all__ = [
     "Todo",
+    "TodoBase",
     "TodoCreate",
     "TodoUpdate",
     "TodoListResponse",
diff --git a/app/schemas/todo.py b/app/schemas/todo.py
index a1c0725..d070513 100644
--- a/app/schemas/todo.py
+++ b/app/schemas/todo.py
@@ -1,6 +1,6 @@
-from datetime import datetime
-from typing import Optional, TYPE_CHECKING
-from pydantic import BaseModel
+from datetime import datetime, timezone
+from typing import Optional, TYPE_CHECKING, List
+from pydantic import BaseModel, Field, field_validator, computed_field
 
 from app.models.todo import Priority
 
@@ -10,23 +10,51 @@ if TYPE_CHECKING:
 
 
 class TodoBase(BaseModel):
-    title: str
-    description: Optional[str] = None
-    completed: bool = False
-    priority: Priority = Priority.MEDIUM
-    category_id: Optional[int] = None
+    title: str = Field(..., min_length=1, max_length=200, description="Todo title")
+    description: Optional[str] = Field(None, max_length=500, description="Todo description")
+    completed: bool = Field(False, description="Whether the todo is completed")
+    priority: Priority = Field(Priority.MEDIUM, description="Priority level")
+    category_id: Optional[int] = Field(None, description="Category ID")
+    project_id: Optional[int] = Field(None, description="Project ID")
+    due_date: Optional[datetime] = Field(None, description="Due date with timezone")
+    
+    @field_validator('due_date')
+    @classmethod
+    def validate_due_date(cls, v: Optional[datetime]) -> Optional[datetime]:
+        if v is not None:
+            # Ensure timezone awareness
+            if v.tzinfo is None:
+                v = v.replace(tzinfo=timezone.utc)
+            # For creation/updates, ensure due date is in the future
+            if v < datetime.now(timezone.utc):
+                raise ValueError('Due date must be in the future')
+        return v
 
 
 class TodoCreate(TodoBase):
-    pass
+    tag_ids: Optional[List[int]] = Field(default=None, description="List of tag IDs to associate with the todo")
 
 
 class TodoUpdate(BaseModel):
-    title: Optional[str] = None
-    description: Optional[str] = None
-    completed: Optional[bool] = None
-    priority: Optional[Priority] = None
-    category_id: Optional[int] = None
+    title: Optional[str] = Field(None, min_length=1, max_length=200, description="Todo title")
+    description: Optional[str] = Field(None, max_length=500, description="Todo description")
+    completed: Optional[bool] = Field(None, description="Whether the todo is completed")
+    priority: Optional[Priority] = Field(None, description="Priority level")
+    category_id: Optional[int] = Field(None, description="Category ID")
+    project_id: Optional[int] = Field(None, description="Project ID")
+    due_date: Optional[datetime] = Field(None, description="Due date with timezone")
+    tag_ids: Optional[List[int]] = Field(None, description="List of tag IDs to associate with this todo")
+    
+    @field_validator('due_date')
+    @classmethod
+    def validate_due_date(cls, v: Optional[datetime]) -> Optional[datetime]:
+        if v is not None:
+            # Ensure timezone awareness
+            if v.tzinfo is None:
+                v = v.replace(tzinfo=timezone.utc)
+            # For updates, only validate future date if it's being set to a new value
+            # Allow None to clear the due date
+        return v
 
 
 # Forward declaration to handle circular reference
@@ -36,9 +64,39 @@ class Todo(TodoBase):
     updated_at: Optional[datetime] = None
     category: Optional["Category"] = None
     project: Optional["Project"] = None
+    
+    @computed_field
+    @property
+    def is_overdue(self) -> bool:
+        """Check if this todo is overdue."""
+        if self.due_date is None or self.completed:
+            return False
+        return datetime.now(timezone.utc) > self.due_date
+    
+    @computed_field
+    @property
+    def days_until_due(self) -> Optional[int]:
+        """Calculate the number of days until the due date.
+        
+        Returns:
+            int: Number of days until due (negative if overdue)
+            None: If no due date is set or todo is completed
+        """
+        if self.due_date is None or self.completed:
+            return None
+        
+        now = datetime.now(timezone.utc)
+        delta = (self.due_date - now).days
+        return delta
+    
+    @field_validator('due_date', mode='before')
+    @classmethod
+    def ensure_timezone_aware(cls, v: Optional[datetime]) -> Optional[datetime]:
+        if v is not None and v.tzinfo is None:
+            v = v.replace(tzinfo=timezone.utc)
+        return v
 
-    class Config:
-        from_attributes = True
+    model_config = {"from_attributes": True}
 
 
 class TodoListResponse(BaseModel):
@@ -50,5 +108,24 @@ class TodoListResponse(BaseModel):
     has_prev: bool
 
 
+class SubtaskCreate(BaseModel):
+    title: str = Field(..., min_length=1, max_length=200, description="Subtask title")
+    description: Optional[str] = Field(None, max_length=500, description="Subtask description")
+    priority: Priority = Field(Priority.MEDIUM, description="Priority level")
+    due_date: Optional[datetime] = Field(None, description="Due date with timezone")
+    
+    @field_validator('due_date')
+    @classmethod
+    def validate_due_date(cls, v: Optional[datetime]) -> Optional[datetime]:
+        if v is not None:
+            # Ensure timezone awareness
+            if v.tzinfo is None:
+                v = v.replace(tzinfo=timezone.utc)
+            # For creation, ensure due date is in the future
+            if v < datetime.now(timezone.utc):
+                raise ValueError('Due date must be in the future')
+        return v
+
+
 # Update forward references
 Todo.model_rebuild()
diff --git a/app/utils/__init__.py b/app/utils/__init__.py
new file mode 100644
index 0000000..67b9db6
--- /dev/null
+++ b/app/utils/__init__.py
@@ -0,0 +1 @@
+# Utils package
\ No newline at end of file
diff --git a/app/utils/date_utils.py b/app/utils/date_utils.py
new file mode 100644
index 0000000..5b7dd1c
--- /dev/null
+++ b/app/utils/date_utils.py
@@ -0,0 +1,78 @@
+"""Date utility functions for todo management."""
+
+from datetime import datetime, timezone, timedelta
+from typing import Tuple, Optional
+
+
+def get_timezone_aware_now() -> datetime:
+    """Get current time in UTC timezone."""
+    return datetime.now(timezone.utc)
+
+
+def get_date_range_today() -> Tuple[datetime, datetime]:
+    """Get start and end of today in UTC."""
+    now = get_timezone_aware_now()
+    start_of_day = now.replace(hour=0, minute=0, second=0, microsecond=0)
+    end_of_day = now.replace(hour=23, minute=59, second=59, microsecond=999999)
+    return start_of_day, end_of_day
+
+
+def get_date_range_this_week() -> Tuple[datetime, datetime]:
+    """Get start and end of current week (Monday to Sunday) in UTC."""
+    now = get_timezone_aware_now()
+    start_of_week = now - timedelta(days=now.weekday())
+    start_of_week = start_of_week.replace(hour=0, minute=0, second=0, microsecond=0)
+    end_of_week = start_of_week + timedelta(days=6, hours=23, minutes=59, seconds=59, microseconds=999999)
+    return start_of_week, end_of_week
+
+
+def get_date_range_next_week() -> Tuple[datetime, datetime]:
+    """Get start and end of next week (Monday to Sunday) in UTC."""
+    now = get_timezone_aware_now()
+    days_until_next_monday = 7 - now.weekday()
+    start_of_next_week = now + timedelta(days=days_until_next_monday)
+    start_of_next_week = start_of_next_week.replace(hour=0, minute=0, second=0, microsecond=0)
+    end_of_next_week = start_of_next_week + timedelta(days=6, hours=23, minutes=59, seconds=59, microseconds=999999)
+    return start_of_next_week, end_of_next_week
+
+
+def get_date_range_next_days(days: int) -> Tuple[datetime, datetime]:
+    """Get start and end of next N days in UTC."""
+    now = get_timezone_aware_now()
+    start_time = now
+    end_time = now + timedelta(days=days)
+    return start_time, end_time
+
+
+def get_overdue_cutoff() -> datetime:
+    """Get cutoff datetime for overdue todos (current time)."""
+    return get_timezone_aware_now()
+
+
+def get_due_soon_cutoff(days: int = 7) -> datetime:
+    """Get cutoff datetime for due soon todos (next N days)."""
+    return get_timezone_aware_now() + timedelta(days=days)
+
+
+def is_overdue(due_date: Optional[datetime], completed: bool = False) -> bool:
+    """Check if a todo is overdue."""
+    if due_date is None or completed:
+        return False
+    return get_timezone_aware_now() > due_date
+
+
+def is_due_today(due_date: Optional[datetime]) -> bool:
+    """Check if a todo is due today."""
+    if due_date is None:
+        return False
+    today_start, today_end = get_date_range_today()
+    return today_start <= due_date <= today_end
+
+
+def is_due_soon(due_date: Optional[datetime], days: int = 7, completed: bool = False) -> bool:
+    """Check if a todo is due within the next N days."""
+    if due_date is None or completed:
+        return False
+    cutoff = get_due_soon_cutoff(days)
+    now = get_timezone_aware_now()
+    return now <= due_date <= cutoff
\ No newline at end of file
diff --git a/requirements.txt b/requirements.txt
index 98f9e19..6932f28 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -4,4 +4,5 @@ sqlalchemy==2.0.23
 alembic==1.12.1
 pydantic==2.5.0
 python-multipart==0.0.6
-ruff==0.1.6
\ No newline at end of file
+ruff==0.1.6
+python-dateutil==2.8.2
\ No newline at end of file