Actually I asked about the similarity between ''by'' and ''around'', but I think that what you've said about ''about'' is also valid for ''around'', right?
One more question, please: is it true that when I say ''you must arrive at 6 p.m." the verb ''must'' changes the meaning of the preposition ''at'', that now will mean ''exactly at''?
Sorry about that - my old teachers used to stress READ THE QUESTION!
Yes, you're right - around and about are interchangeable when we're talking about times.
You're correct,too about at. ........arrive at six means arrive on the dot of six o'clock. (You don't really need the must for this to be the case.)
You should arrive by 6.
You must arrive by 6.
It's recommended that you arrive by 6.
It doesn't matter how "strong" the suggestion is: "by" 6 means that when 6 o'clock rolls around, you need to be there.
You should arrive at 6.
You must arrive at 6.
It's recommended that you arrive at 6.
In each case, that means on-the-dot at 6. (In fact, 5:58 would be okay too, but I still wouldn't be there at 6:02.)
I had a class the other day and the teacher left my mind in a mess. I used to think that I knew what ''by/at time'' meant, but now I am not that sure.
Is it correct to say that:
"by 6" - you can arrive any time you want as long as when it's 6, you must be there;
"at 6" - you cannot arrive after 6 and you cannot arrive too earlier than that.
I was wondering if ''at 6'' is really effective. It's very difficult to arrive at an appointment on-the-dot. People usually arrive 5 minutes earlier, or even before that, in order not to be late. So, in fact, everybody always arrive "by 6", don't you think?
I wonder what are the real implications of "by/at time" in the real life.
Sure, but you can say "the movie starts at 6." It doesn't start earlier or later.
The show starts at 7 but they don't open the doors until an hour before. Since it's going to be raining tonight, try to arrive just at 6 so you can get a good seat but don't spend too much time in the rain.
The train leaves at 7, but I want to be there by 6:45 just to be sure we don't have any trouble.