how to use postpone and delay?

You use the word postpone in a formal manner such as a business meeting or a test. You also use the word when you already have a definite time and date. One example would be " The business meeting would be postponed and moved to....so and so" The word delay is usually used more on unexpected circumstances such as " their has been a delay in our flight" It is also used on short term circumstances like "time delay mechanism" that's why we do not use " time postponement mechanism" Hope I answered the question correctly