datetime in defining database using sqlalchemy

Should I use () with datetime.now in defining tables? What code wrong 1 or 2?

1:

Base = declarative_base()
class T(Base):
    __tablename__ = 't'

    created = Column(DateTime, default=datetime.now)

2:

Base = declarative_base()
class T(Base):
    __tablename__ = 't'

    created = Column(DateTime, default=datetime.now())