My friends daughters year long lease is ending the 31st of this month. The landlord is telling her that she has to be out at the beginning of the day of the 31st. This would be the day that she would be moving out and finishing her cleaning? Is it correct that she has to be out in the morning of the 31st like the landlord is demanding or does she have until midnight of that day?

If her lease runs through the 31st, then she can legally stay there until midnight that day.

That is, as long as she didn't give a dated notice stating that she would be out before the 31st?

If she really can't get out as soon as the landlord wants, be sure to get excellent documentation of the condition of the apartment as this could piss the landlord off enough that they may try to eat up her deposit. Take photos, videos, have someone walk through with her to point ANYTHING that would deduct from the deposit so she can correct it prior to her turning in the key.

Good luck.

It may state in the lease when she needs to be out. For example, my current lease says I will need to be out by 5 pm on the last day. Also, in most cases the apartment isn't considered surrendered until the keys are turned in, and no landlord is going to accept them at midnight. So I'd go look at the lease and see what it says, and then decide how much you want to fight this. Is it really that much more trouble to move out the day before? If it is, fight. Otherwise, I'd just go along with it.