How to postpone the interview
If you already have a specific interview date, but you have a good reason why you can not visit it, try to reschedule the meeting. Colds and flu with all the attendant symptoms (runny nose, coughing and sleepy appearance) are unlikely to promote approval of your candidacy. In addition, you can infect the interviewer. A serious illness of a member of your family, the breakdown of communication systems in the apartment and other circumstances are enough weighty arguments for postponing the interview time.
The most optimal way to notify the employer about changing the date of the meeting is a phone call or sending a letter by e-mail. Try to inform the management of the organization, who invited you to the meeting, as soon as possible. So you show that you appreciate not only your own, but someone else's time.
In the message, give your name and the name of the person who invited you to the interview. then name the reason why you can not come. Complete the message or conversation with the expected date for the new meeting, wondering at the same time what time it will be convenient for the employer. If the competition for the position is large, the company management has every right to refuse to postpone the interview date.
If, after going to a meeting, you feel that you will be late (hit the traffic jam, the car broke down, etc.), report your delay and its reasons on the phone as early as possible. At the same time, the employer has the right to offer you to postpone the meeting, since your delay may violate his working schedule.
If there is a slight delay, without a preliminary call, calmly apologize and admit your own wrong. Stick with dignity and watch the reaction of potential superiors. The leader, who showed rudeness and irritation to the applicant, will probably also behave with the subordinate.