Why walmart split my day off ?

You would have to have a chat with your manager and ask them, if you need to fix it find out if they can do that. 

This sounds like a question you should ask your boss.

Because a computer figures out the schedule and computers don't know or care about how humans need rest.

Managing resources during this difficult business climate.  Many big box stores have done just that. Brother in law works for Lowes, same ****.