diff --git a/cogs/commands/set.py b/cogs/commands/set.py
index a9b55b3..0b5925d 100644
--- a/cogs/commands/set.py
+++ b/cogs/commands/set.py
@@ -6,7 +6,8 @@ from datetime import datetime
 
 import nextcord
 from nextcord.ext import commands
-from sqlalchemy import delete
+from sqlalchemy import delete, select
+from sqlalchemy.exc import IntegrityError
 from sqlalchemy.orm import Session
 
 from dakiny_bot import birthday_list
@@ -45,22 +46,40 @@ class setCog(commands.Cog, name="Set Commands"):
             day (int, optional): The day a user was born. Is SlashOption.
         """
 
+        # Must be deferred, apparently datetime takes a little bit on invalid dates.
+        await interaction.response.defer(ephemeral=True)
+
         if month == 0 and day == 0:
             stmt = delete(UserBirthday).where(UserBirthday.UserId == interaction.user.id)
             with Session(engine) as session:
-                session.scalar(stmt)
+                session.execute(stmt)
                 session.commit()
+                await interaction.followup.send("Removed birthday.", ephemeral=True)
                 return
 
         # check if valid day
         today = datetime.today()
-        birthday = datetime(today.year, month, day)
+        try:
+            birthday = datetime(today.year, month, day)
+        except ValueError:
+            await interaction.followup.send(f"Invalid date: {month}/{day}.", ephemeral=True)
+            return
 
         # If the birthday is today, add to birthday_list
         if today.date() == birthday.date():
             birthday_list.append(interaction.user.id)
 
-        new_birthday = UserBirthday(interaction.user.id, f"{month}/{day}")
+        new_birthday = UserBirthday(UserId=interaction.user.id, Birthday=f"{month}/{day}")
         with Session(engine) as session:
-            session.add(new_birthday)
-            session.commit()
+            try:
+                session.add(new_birthday)
+                session.commit()
+            except IntegrityError:
+                # User already has birthday, change it instead.
+                session.rollback()
+                stmt = select(UserBirthday).where(UserBirthday.UserId == interaction.user.id)
+                new_birthday = session.scalar(stmt)
+                new_birthday.Birthday = f"{month}/{day}"
+                session.commit()
+
+        await interaction.followup.send(f"Birthday set to {month}/{day}.", ephemeral=True)