be here AT 8:00am and be here by 8:00am?
There really isn't any PRACTICAL difference.

Grammatically though, "Be here AT 8:00am" means "I don't care where you are at one second before 8:00am, nor do I care where you are at one second past 8:00am, but on the dot of 8:00am, be here". Whereas, "Be here BY 8:00am" means "arrive at some point in time before 8:00am, and remain here until at least 8:00am".

Like I said, there's very little difference really in practice, although the "by" version could be taken to imply a little more flexibility - like, if either of us is a little late, we wait for the other, wheras the "at" version could be taken to imply "if you're late, you'll have missed it".

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When you plan to carry out something for a specific time at the latest. Use ' by 'Emotion: smile

eg. Try to finish what I've told you by 9 o'clock.

' at ' in the sentence simply tells a time
Could I say I was here at 8.00 sharp?
What's wrong with thatEmotion: smile, perfect sentence. Mentioning the time would be even better though.

eg. I was here at 8.00 sharp the other dayEmotion: smile
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