Exemplo de Formatação de data no ModelAdmin

gistfile1.py

    # def expiration_date(self):
    #     return self.expiration_date.strftime("%d/%m/%Y")
    # expiration_date.short_description = 'data de vencimento'
    #     
    # def payment_date(self):
    #     return self.payment_date.strftime("%d/%m/%Y")
    # payment_date.short_description = 'data do pagamento'


ou

-- settings.py

USE_L10N = False
DATE_FORMAT = 'd/m/Y'
SHORT_DATE_FORMAT = 'd/m/Y'
DECIMAL_SEPARATOR = ','