If in the highly unlikely event, is in one of these situations, all we can do is communicate openly and honestly with your prospective employer, apologize and explain the situation and hope that you have not had too detrimental effect on your employment opportunities.
The truth however is that no matter how good and proper that there is a reason for the rescheduling will not be professional, organized and reliable, as you would have done if you had appeared at the time that you had first settled.
You must remember that your future employers are not stupid and gullible, so do not follow the path to invent a reason to reschedule. It is highly unlikely that you believe and no one likes a liar. All you can think of excuses that have been used and seen for the umpteenth time.
Life is life, though, and things can go wrong in the day - silly things like the alarm does not go or stay stuck in traffic or miscalculate the traveling time to the interview. Of course it is very easy to point that should not have allowed any of these happen, but if things go wrong, all you can do is go into damage limitation. Get in touch directly with the employer, preferably before the interview time and hope to reschedule. Do not be surprised if you do not get the response he wanted.
You really have to see from a perspective employer. Would you like to hire someone, agreeing to pay them a salary and give those responsibilities that are important to your business, if not even show the organizational capacity, reliability and good attitude to stick to a job interview time?
