About Password Policy

Hi,
I have a question that in active directory we set password policy “Enforce Password History” and user has to keep password for a day. When user is trying to change the password from his/her pc she gets error message.
But we can change the password through Active Directory Users and Computers and at that time we don’t get error message even if we give same password.
I want to know why we don’t get error message but users gets it.
I hope you understand my question.
Thanks and Regards.
Anurag.