It all depends, within a day, cool....when you're getting READY for said date...not cool at all. I knew of a female friend that was getting her nails done (for the date), only to have the guy text her while she was at the salon and couldn't make it.
She got home, saw the "Online Now" under his screen name and she gave him a piece of her mind. lol.
Most women get their nails done regardless...she may have moved the appointment up but chances are she does it anyway regularly.
If you plan a date around the person you're meeting it can be frustrating for them to cancel. Being able to go anyway, or having a plan B and C (if you don't want to stay home) is a good way not to let cancelling bother you, even last minute.