Modals, should be present tense or present perfect tense?

about the following dialoque:

A: what time is it?
B: Well, we came at seven, and I’m sure we’ve been here for at least an hour. So, it must have been around eight o’clock.

My question is if the answer goes " it must be around eight o’clock.", Would it be correct?

What time is it?
It must be around eight o’clock.

  • is fine.

The expanded reply has mixed tenses. The whole sentence should read
Well, we came at seven and I’m sure we’ve been here for at least an hour, so it must be around eight o’clock.

Hello,
Thank you for the above explanation. two more questions: if “…so it must have been around eight o’clock.” and " it must be around eight o’clock." are both correct. Do they express the same meaning? and, Which one is more common?

Hi Ha269,

There is a difference between ‘It must be’ and ‘It must have been’. As you know, ‘must’ is a so called defective verb because it can’t make a past tense, has no continuous form and has no past participle, which is possible with other verbs. The only way it can indicate the change of tense is through the following infinitive.

In this sentence we are talking about ‘now’: Yesterday was Wednesday and so it must be (present)Thursday today.

In this sentence we are talking about ‘then’: We went to school two days ago and so it must have been (past)Tuesday.

Alan

Hello, Alan

Thank you very much. I understand the two sentenses you worte above, but I still not quite understand the dialoque: A: what time is it? B: Well, we came at seven, and I’m sure we’ve been here for at least an hour. So, it must have been around eight o’clock.

if “… it must have been around eight o’clock.” indicates the past. how can it cope with " what time is it?" ? “what time is it?” is present tense. I am still confused.

Ha269

Hello Ha,

As I indicated in message #2 the response ought to be ‘it must be around 8 o’clock’.
‘Must have been’ doesn’t work in this context because the question makes it clear that 8 o’clock is the present time. 'must have been ’ is incorrect.

Hello, Beeesneees,

Thank you very much for the help. now I know I was confused by the wrong answer of my grammar book.

by the way, you and Alan have a good weekend. Thank you all very much.

from ha269