I am able to add a new value to a time field successfully. But when I am trying to update the same row, the update is happening in the backend, but not reflected in the UI

Hi

please try 

 a!refreshVariable() with refreshOnVarChange

Please take a look at this thread, as it appears to describe a similar issue to the one you're experiencing.

https://community.appian.com/discussions/f/user-interface/18504/datetime-field-issue-updated-value-is-not-displaying

We need a lot more detail about what you're trying to do, how you're trying to do it, and what you expect to have happen (versus what actually *is* happening, be it "nothing" or just something you weren't expecting).  Sample code?  Screenshots?  Anything more would be helpful.