One way is if you are on the birth control pill. Skipping the white pills (colors may vary) or blanks as we know it, will cause you not to have a period.
A delay is a "push back" on the set time. When a school gets a delay, they "push back" the time that they had originally chosen due to whether or other possibly dangerous things. Hope this helps(:
It depends if your cycyle is regular or not. In every case to confirm the pregnancy you should do the test. It worths to wait another one week before doing the test.
There are a lot of ways to delay it. I heard that eating lemons would help to delay it for a day or two. Sometimes when women are anxious or worried they get it later then they are supposed to, but...