Dell delivery system disappointed me

I ordered a laptop on 23 July.
The estimated time of delivery is 30 July at first, which is 6 business day.

Dell term states that they'll be delivering the laptop between 5 till 8 business days.

Then for no reason, they changed the estimated delivery to 13 AUGUST!!
WHAT THE @#$%!!!

If I want to sue them I think this is a valid reason since they already state that the'll deliver within 5 till 8 days.

And the laptop is needed urgently as i need it to do my university works.

Are there some people experience the same thing before?