Question

How can we know the time at night without clock or watch

Answer 1

we can know the time at night by phone.

Answer 2

It is possible , but this has not been tried yet due to the lack of technology.

We know that the earth rotates , this makes the sun set and rise.
The same occurs even for moon known as moon occurrnce and moon set.
During night , we can locate the exact time by the position of the moon.

The drawback is that moon is not stable like the sun relative to the earth.
So there will be a lag.
This would be like seeing the sun right above our head at 5 pm.

So a technology must be created to locate the apparent position of the moon as well as the stable position of the moon.

One more drawback is the shades that the moon gives.
On a no moon day we will never be able to find the time.
Hence we use clocks.