3. A.M. and P.M. What is Noon and Midnight? A.M. and P.M. start immediately after Midnight and Noon (Midday) respectively. This means that 00:00 A.M. or 00:00 P.M. (or 12:00 A.M. and 12:00 P.M.) have no meaning. Every day starts precisely at midnight and A.M. starts immediately after that point in time e.g. 00:00:01 A.M. To avoid confusion timetables, when scheduling around midnight, prefer to use either 23:59 or 00:01 to avoid confusion as to which day is being referred to. It is after Noon that P.M. starts e.g. 00:00:01 PM (12:00:01)
4. Native English speakers seldom say "good day" anymore. We say whichever greeting feels appropriate for the moment.If I woke up at 1:00 in the afternoon, I might say to someone, "Good morning," or they might say it to me. It's ironic, but we do say it.Some people say, "Good morning," only after they get out of bed, and then say "hello" or "hi" for the rest of the morning and the entire afternoon and evening. Until I was an adult, I never said, "Good morning," to anyone other than my family, because no one else saw me right after I got out of bed.Many people day, "Good morning," the first time they see you during the work day, but after the first half-hour or hour they would switch to "hi".People seldom say, "Good afternoon," or, "Good evening," except in very official situations when they are addressing a group, or when they're imitating a villain from a monster movie or some similar character.People usually say, "Good night," right before bed time. However, many people also say, "Good night," at 5:00 when they leave work. If someone works the midnight shift at a factory, and he goes to bed at 8:00 in the morning, we say, "Good night," to him then.
