How to extract correct data from Sqlite database using Python?

I have a database of people names and their birthdays. The format of birthday is mm\dd\yyyy, like "3\13\1960".

I want to extract a list of people whom born after a specific date. I called this date "base".

The program that use see below, firstly create a DB of people, and then extract the required list. The problem is the result is not as I expect:

import datetime as dt
import peewee as pw
db = pw.SqliteDatabase('people1.db')

class Person(pw.Model):
    name = pw.CharField()
    birthday = pw.DateField(formats=['%m/%d/%Y'])
    class Meta:
        database = db # This model uses the "people.db" database.

db.create_tables([Person])


bob0 = Person(name='Bob0', birthday='4/13/1940')
bob1 = Person(name='Bob1', birthday='5/13/1950')
bob2 = Person(name='Bob2', birthday='3/13/1960')
bob3 = Person(name='Bob3', birthday='3/13/1970')
bob4 = Person(name='Bob4', birthday='3/13/1980')
bob5 = Person(name='Bob5', birthday='3/13/1990')

base = Person(name="base", birthday='3/13/1960')

bob0.save()
bob1.save()
bob2.save()
bob3.save()
bob4.save()
bob5.save()
base.save()

for item in Person.select().where(Person.birthday > base.birthday):
    print item.name , item.birthday

Output:

>>> ================================ RESTART ================================
>>> 
Bob0 1940-04-13
Bob1 1950-05-13
Bob3 1970-03-13
Bob4 1980-03-13
Bob5 1990-03-13
>>> 

As you see above, base = 3\13\1960. So I shouldn't have Bob0 and Bob1 in output! How can I handle it?

Note that, I don't want to change the format of birthdays in database. I also don't want to fetch all the rows and check them later! I want to fetch the required rows only.