Cleft sentences,which is correct?

[Hiya Raymond]

1. It was on January 31st that he came here last time.
2. It was January 31st when he came here last time.
3. It was January 31st that he came here last time.
4. It was on January 31st when he came here last time.

5. It was last night that it snowed.
6. It was last night when it snowed.

7. It's Joey (whom) we're looking for.
8. It's Joey (that) we're looking for.

Are all of those sentences grammatical? Cleft sentences or attributive clauses? Thanks a lot!

 

[emsr2d2]

1. It was on January 31st that he came here last time.
2. It was January 31st when he came here last time.
3. It was January 31st that he came here last time.
4. It was on January 31st when he came here last time.
It was on January 31st that he last came here.
It was on January 31st that he came here last.

5. It was last night that it snowed.
6. It was last night when it snowed.
It was last night that it snowed.

7. It's Joey (whom) we're looking for.
8. It's Joey (that) we're looking for.
It's Joey that we're looking for.
It's Joey we're looking for.

Thanks!

See my comments/suggestions above in red. Note that when you number a list, you should put a space after the full stop after the number - I have edited your post to show it correctly.

 

[Hiya Raymond]

Are 1 ，2 and 7 grammatical?
If "It's Joey that we're looking for." is a cleft sentence,why 'that' is omitted ?

Thanks!

 

[Hiya Raymond]

Are all of those sentences grammatical? I'm confused!

 

[emsr2d2]

Are 1 ，2 and 7 grammatical?
If "It's Joey that we're looking for." is a cleft sentence,why 'that' is omitted ?

Thanks!

I have no idea why I only gave the third sentence with the "that" omitted. It can be omitted in all of them.