Timezone-naive datetime

The snippet

# Stores user signup timestamps. Works on the dev machine.
from datetime import datetime

class UserStore:
    def __init__(self):
        self.users = {}

    def create(self, user_id, email):
        self.users[user_id] = {
            "email": email,
            "signed_up": datetime.now(),
        }

    def signed_up_today(self, user_id):
        u = self.users.get(user_id)
        if not u:
            return False
        return u["signed_up"].date() == datetime.now().date()

What would a senior flag FIRST?