It's not or it isn't

[timeserved]

As per title.
To say:

It is not lunch time yet
It is not urgent
etc
if you like "it's not" vote UABU, or it isn't UANBU

Either is fine.

Both ok

Depends where you want to put the emphasis.

You might also say “ ‘t’nt lunchtime yet”..

It’s t’int in our house 😁

I only say "it is not" when I want the not to be really emphatic otherwise it sounds a bit Data.

I'd probably say it ain't lunchtime yet 😂

“Not lunchtime it is.”

… but then I’m a tiny green wizened alien.

Both are perfectly ok.

Do forget 'it ain't' (always follow with guvna at the end of the sentence for correct grammar)

Can we please include b'ain't, as in "it b'ain't snowing yet round 'ere" (SW England) 😀

I say it isn’t because when I say it is not I sound like a robot.

Also I’m a robot sounds less like a robot than I am a robot

'tain't round here

And if b'ain't, followed by "be um?"
(Slightly "posh" part of SW here 😄)

Emphasis is the main one

so say someone asks you if it is lunchtime yet and it’s 11:45 you say no it is not because you are saying of course it’s not it is way too early. 12:30 would be no it isn’t because they is a far more neutral response.

can you do this task - again it would not no it’s not urgent because you are emphasising the fact there is no need to do the task right now.
do you need to do this task would be no it isn’t urgent

the majority of the time it is it isn’t it’s not is making a point (and that can be somewhat passive aggressive if used in a certain way)

Either will do. But if you want to sound outraged, “it is NOT!”

In spoken usage, contraction is normal. Same for written usage in speech marks, unless speaker is emphasising ‘not’ [eg ‘it is not lunchtime yet’]. In written form, especially formal texts, then no contraction is the usual format.

There is no ‘preference’ - usage depends on context and whether written or spoken.

Odd thing to post about, really.

Round here it would be 'it's no lunchtime yet' 😄

Why is it an odd thing to post about? Odd remark!

Its T'ay where I am

Either is acceptable

Not at all. A quick google enquiry would explain appropriate usage of contractions as would any online dictionary.

Have lunch you will not.

I don't think OP is asking about not contracting i.e. saying "it is not" like a robot. She's asking whether you prefer to use the contraction "it's not" or the contraction "it isn't"

Either. Maybe one more likely than the other depending on emphasis but it’s not a distinction I notice in my own speech let alone other people’s.