Is there a way to visualize curvature of time? I mean curvature of space is both mathematically and physically is comprehensible. I have doubt about curvature of time.
If you are thinking of spacetime as a product of a three-dimensional space $S$ with one-dimensional time $T$, then time is necessarily flat, because all one-dimensional manifolds are flat. So no, there is no way to visualize the curvature of time separately from the curvature of space, because there is no such thing as the curvature of time separately from the curvature of space.
Here's one simple visualization. Imagine that the surface of the earth is spacetime. Time points north. There is one space dimension, which points east-west.
Imagine two objects with worldlines that point north. Such worldlines are geodesics, meaning the objects are unaccelerated. At the "equator" time, they are at rest with respect to each other, in the sense that their spatial separation is (instantaneously) not changing with respect to time. As we follow the worldlines farther and farther north, we find that their spatial separation begins to decrease! This effect arises purely due to curvature, and the interpretation is that gravity is pulling these objects together.
Spacetime isn't really a sphere, but hopefully this gives you an idea for what it means for spacetime to be curved.
Space and time are both concepts strongly related to an Euclidean vision of the world around us: in the proper sense they do not curve singularly. It's spacetime that curves and doing so it determines the properties and characteristics of the universe.
I think it's important to stress this point in order to visualize correctly the curvature of spacetime. Other than that, I haven't really understood your question.