It's 4:00 by that clock

[Daruma]

Hello.

- It's 4:00 by that clock.
- It's 4:00, by that clock.
- It's 4:00 on that clock.
- It's 4:00, on that clock.

Which is correct?

[bhaisahab]

Hello.

- It's 4:00 by that clock.
- It's 4:00, by that clock.
- It's 4:00 on that clock.
- It's 4:00, on that clock.

Which is correct?

The first two are correct. Can you tell the difference between 1 and 2?

[Daruma]

The first two are correct. Can you tell the difference between 1 and 2?

Could you tell me the difference, please?

[bhaisahab]

Could you tell me the difference, please?

You are in a place where there is only one clock, your friend asks you 'What time is it?' You say 'It's 4 o'clock by that clock.' If there are two or more clocks, you might say 'It's 4 o'clock, by that clock (but it's 10 past 4 by the other one).