Which way of confirming time is best expressed?

[Anonymous]

No worries, you may rest assured that I will be there at the appropriate time at 12pm as its suggested.

Please rest assured that I will be sure to arrive at the appropriate time of 12pm.

[Anonymous]

Like its an ordinary part of life. Which is to say, short, concise and without ceremony.

"Confirmed, 12pm on the 5th of April. Thanks."

If its confirming with someone whos a date, you could go for:

"Exited to see you, will be there (Friday) at 12pm sharp!"

The two ways you cite seem they could work if your confirming a funeral or something similarly somber.

The second reply sounds more chastising of them suggesting you may be other than on time.

[Siri137]

The first sentence.

[laly520]

second