The clear-cut rules for cancelling a hotel reservation can
simply be applied for cancelling a date - it is all about
If you pull out more than a fortnight beforehand, there is no penalty at all; between a week and two days' beforehand, there are varying but small amounts of fallout; anything less than 48 hours and you start to incur hefty charges; and if you cancel on the same day or, rudest still, fail to show up altogether, then you have to pay the full price. Hotel rooms may be expensive but romance has been known to founder on such cavalier behaviour.
Always apologise profusely, even if you're not actually sorry you're pulling out. Cancelling once (following the timing rules above) is generally accepted; constantly postponing a date ends up being rude and hurtful.
If your cancellation is for genuine reasons and you fear you may have offended, you could send some flowers or other suitable gift to reiterate your regret.
Standing someone up is the height of bad manners. If you have been stood up don't jump to conclusions, there may be a reasonable explanation. Make a call after about half an hour of waiting to find out what's gone wrong. If there's no answer you can suspect the worst. Maintain your dignity and don't leave an angry message. Consider yourself lucky and move on.